Fundamentally, a cloth diaper is made up of an absorbent inner material and a waterproof exterior material.  The absorbent inner material may or may not be topped with a fabric that provides a “stay dry” layer to keep moisture away from baby’s bum.  It might seem obvious: waterproof piece and absorbent piece; but all the differences in cloth diaper types boil down to what waterproof material is on the outside, and which absorbent materials and/or stay-dry layers are on the inside.

Waterproof Outer Options:

Polyurethane Laminate:  The vast majority of modern cloth diapers have an exterior made of Polyurethane Laminate, commonly referred to as “PUL.” PUL is waterproof and comes in a wide variety of prints and colours.  Less common is a material called TPU, Thermoplastic Polyurethane, which is similar to PUL.

Wool:  Yes, wool! Sheep have a natural protection against moisture: their wool!  Diaper covers made of wool are often called soakers, shorties or longies.  On top of an absorbent fitted diaper, a wool cover is a favourite night-time solution for many, while others love a lighter wool cover even during the day!  Wool covers are not washed after each use: urine is neutralized when it comes in contact with the lanolin found in wool.  To maintain its efficiency, wool is washed and lanolized around once a month.  A special wool wash or even baby soap can be used to gently hand wash wool, and the addition of lanolin to the wash water will make the wool water-resistant again.

Fleece:  Ever noticed what happens to water when it hits your fleece jacket? It just sits on the surface of the fabric, right? Fleece covers work the same way, and are washed after each use.

Absorbent Inner Fibres:

Microfiber is a very common material for cloth diaper inserts.  The microfiber material used in diapers is just like the material you use to dust or clean up spills at home.  It is highly absorbent and very inexpensive.  Note that microfiber is only used in combination with another fabric on top, since microfiber should not come into direct contact with baby’s skin.  (If you touch a microfiber insert with your fingers, you’ll feel how the fibers grab at your skin: we don’t want this effect on baby’s bum.  Also, microfiber is so absorbent that it will suck moisture out of baby’s skin.) Microfiber inserts come in a variety of sizes, and many can be snapped down to make them shorter and add layers of absorbency.

Cotton is a very absorbent natural fiber used in many diaper brands and also for flat and prefold diapers. When peed on, cotton stays very wet to the touch. For some babies, a stay dry layer between the skin and the cotton is necessary to keep rashes at bay. When it is potty-learningtime, the fact that the child can feel when he is wet can help him understand when it’s time to go!

Bamboo is a highly absorbent natural fiber that is usually blended with cotton to make inserts or even the entire inner of a diaper or as the main material in a fitted diaper. You might see bamboo in a “terry” form, with a loopy texture to it, or “rayon from bamboo” which is smooth to the touch and looks almost like a t-shirt knit.

Hemp is often touted as being one of the most eco-friendly fibers available. (http:// greenopedia.com/article/why-hemp-so-important) It is extremely absorbent and is blended with cotton to make inserts or fitted diapers.

Fleece, suedecloth, or polyester mesh are commonly used as the "stay-dry" layer in cloth diapers.  Fleece can be used as a liner, and laid on top of the diaper (great for easily dumping solids into the toilet) or it may be the actual top material of the pocket diaper or insert for an AI2 system.

Categories of Diapers:

Diaper cover/wrap/shell: A cover is used with a fitted diaper, insert, prefold or flat diaper as the waterproof layer.

All-in-one Diaper (AIO): A diaper that is entirely one piece: the exterior, waterproof PUL is attached to the interior, absorbent portion.  AIOs come in a variety of designs, but most have an insert sewn directly to one end of the diaper, and an additional booster that can be snapped in as needed.

All-in-two Diaper (AI2) or Hybrid:  An AI2 is any diaper system in two pieces: the waterproof shell (also called a cover or a wrap) and the absorbent insert.  The insert may be a prefold or a trifold, or a rectangular insert or even an hourglass shaped insert.  You lay the insert inside the diaper before putting it on baby.  When it’s time to change, as long as the cover isn’t soiled, you can simply put in a new insert rather than changing the whole diaper. Some brands have snap-in inserts (GroVia, Best Bottom), but that doesn’t mean you can’t mix and match brands.

Pocket:  A pocket diaper has a layer of fabric sewn directly to the outer PUL exterior. There is an opening in this layer of fabric (a pocket!) where you stuff in the absorbent insert of your choice. When it’s time to change, you change the entire diaper.  For most brands, you pull the insert out of the pocket before putting both pieces in the wash bin.

Fitted:  A fitted diaper is a diaper made entirely of absorbent material that is secured around baby with snaps or Velcro.  A fitted diaper requires a PUL cover, fleece cover or a wool soaker.  Fitteds can be a great option for overnight.

Prefold:  Prefolds usually come in at least three sizes, and can either be folded into a rectangle and laid inside a cover, or you can lie baby on the prefold and use a variety of folds to secure the diaper around baby prior to putting on a cover.  Most prefolds have more layers of fabric in the middle. You don’t need diaper pins: a Snappi will hold the diaper in place!

Flat: A flat diaper is a large piece of absorbent fabric that is the same thickness throughout (usually 2-ply) that is folded more elaborately than a prefold and secured around baby.

(Trifold) insert:  A trifold insert is a rectangular piece of absorbent material that is folded (usually in three) to create multiple layers of absorbency.  The insert can be folded to fit perfectly either in a pocket diaper or in a shell.

Accessories:

Snappi:  A snappi is used in place of diaper pins to secure a prefold, flat diaper or snapless fitted around baby.

Wet bags / Pail Liners:  Wet bags and Pail Liners are made of PUL and are meant to contain soiled diapers.  Wet bags come in a variety of sizes, from a very small one to carry one or two dirty diapers, to a large one to store your diapers until wash day.

Wipes:  Cloth wipes are a natural extension of cloth diapering, and can help you eliminate disposable wet wipes.  You can wash your wipes along with your diapers. 

Liners:  Liners are meant to “catch” the solids and allow you to easily dump them in the toilet. Resusable liners are usually made of fleece. Disposable liners can be flushed along with the solids.

Boosters/Doublers:  These are smaller rectangles (sometimes hourglass shaped) of absorbent material meant to boost the absorbency of any type of diaper for overnight, naps or heavy wetters.