The three wheeler pushchair:

Looks trendy, a great pushchair to have especially if you live near the countryside and do a lot of walking. They are not usually suitable from birth although you can get attachments to adapt them. They are very easy to steer.

Four wheeled Forward facing pushchair:

Light and maneuverable and can have a lie back facility suitable for newborn babies. Some are lighter than others.
Buggies and strollers:

Many are not suitable for the very young babies as they do not have back support although some do, check before you buy. Robust and lightweight.

Two-in-one pram / buggy:

Can be used in the lie flat position in the same way as a pram and also as an upright buggy. Some allow you to face baby towards you with a reversible body which you will find a comfort for young babies for the first few months.

Three-in-one:

Just like a 2 in 1 but with a separate detachable carrycot.

Travel System pram / pushchair:

Some Prams or pushchairs also have a detachable carrycot system, and come with a clip-on car seat; these are great for keeping a baby asleep when transferring to or from the car.

The good old fashioned upright pram:

Grandparents love them, comfortable for baby - but your child will quickly grow out of it, babies as early as three months old are very keen to look out and about and they take up a lot of room when you need to store it away.