A trainset is one of the best ways to start in the model railway world.  It has all you need to begin.

Including
a variety of locomotives, rolling stock, enough track to make and oval
(some with sidings as well), and a powered control system be it either
analogue or digital. Most importantly, each includes instructions to
guide you in the set up and also ideas to extend the model empire.

All sets are fully expandable and the compatibility between brands gives the modeler a vast choice.

Train
packs are usually a train consist, i.e a loco and rolling stock, or
just a group of rolling stock alone. These do not include a controller
or track and are a good way of adding a train to an existing layout.
Also, they give a range of choice of trains not available in trainsets
selection in which you can then buy a track set and controller
separately.

Drop into Branchline have a browse around the site to see the full range available.