This page is a brief guide to the nappy jargon of washable nappies

Most modern washable nappy systems consist of a nappy (the absorbent bit) and a waterproof wrap (also known as a cover) that goes over the top to keep the nappy from touching the clothing and getting everything else wet.
Having two leg and waist barriers (1- the nappy, 2 - the wrap) gives excellent containment - if the nappy leaks onto the wrap, the wrap will stop everything else getting soiled.

Nappy + wrap = dry baby!

There are also liners – these are made of polyester fabric usually polyester fleece, or paper, and designed to go inside the nappy to catch the poo and often to keep baby feeling drier

Fleece liner: Benefits – keeps baby drier, reusable, will also protect the surface of the nappy from the worst of the stains.
Flushable liners   : Benefits -  good for wiping poo off, are made of paper and can be flushed hence they're easier for out and about.
For newborn breastfed babies – as breastmilk is designed for babies there is initially at least very little solid matter.  Thus poo will soak through paper liners, leaving little waste material on top for disposal – a bit like a smear of curry paste!  At this stage many parents opt not to use a liner, and the washing machine will wash it out, later with more volume of poo to contend with, many parents opt to rinse this off in the loo. (Newborn bottlefed babies tend to have more solid poo, so for them a liner may be more useful)

You’ll also come across boosters – pads of fabric to add to a nappy system for extra absorbency if needed, you can add these either inside the nappy or between the nappy and the wrap (the latter is particularly once the nappy is beginning to get outgrown, as it'll help the fit of the nappy and prevent leaks).

The nappy can either be a

flat nappy such as terry squares, muslins or prefolds, that need a bit of folding to fit, and is usually secured with pins or with a stretchy gadget called a Nappi Nippa that hooks the nappy together

or a

shaped or fitted nappy such as Tots Bots, Kissaluvs, Bimble usually that has elastic at the legs and waist, and either fastens with poppers or Velcro, or secures with pins or a Nappi Nippa

Many nappies are sized, in that throughout baby’s time in nappies you might need two or three sizes to fit from newborn to potty training. Alternatively they can be one size or ‘birth to potty’ such as Motherease One Size that will fit an average baby all the way through (but may be bulky on a newborn, or outgrown on a larger or older child before potty trained).

Of course to confuse the issue further, for some nappies such as Tots Bots Bamboozles or Nature Babies Diddy Diapers the larger size nappy can be folded down to use as a one size by folding the front over outwards to reduce the height, and fastening the tabs with a Nappi Nippa making it small enough for a newborn baby.

Finally there are nappy systems that combine the nappy and wrap together in one piece and are called all in ones – examples Motherease All in One, Kooshies Ultra. It's worth considering that for a newborn with scrawny legs and runny poos, unlike the nappy + wrap scenario above, with an all in one there's only one barrier, so whilst all in ones might seem easier to use they can be less efficient on containment till your baby is bigger.All in ones can be slow to dry as the absorbent bit is partly covered with waterproofing on one side

Consequently, from this a further type of nappy system has emerged over the past 5 years: the pouched nappy system.  This effectively consists of a wrap with an inner liner of non absorbent soft polyester fleece sewn in leaving one end open to form a pouch.  Into this pouch can be stuffed a folded flat nappy (such as a trerry square or a prefold) or an absorbent pad or insert – these pads are often made of microfibre for quicker drying, or can be cotton, hemp or bamboo.