As a model railroader, you will have to make choices about your layout. It's best to sit down and make these choices beforehand, rather than figuring them out along the way. It will keep you from having to redo things in the future. One of these choices is DC or Digital Command Control (DCC). This will affect the type of locomotives and track accessories you buy, and how you wire your layout. I recommend DCC, and this article will explain why.
Before Digital Command Control, modelers were fairly limited in how complex they could build their layout. There would be a power unit that would produce an electrical current on the tracks, and the trains would pick up this current and run. The power unit would apply more voltage to the tracks if you wanted the train to speed up, and less voltage if you wanted the train to slow down. The problem is that if you have more than one train on the tracks, both trains would respond the same way. A way around this would be to have sections or blocks of the layout isolated from each other, and through combinations of power switches, you could control more than one train. This required a deeper understanding of electricity, and a lot of time spent troubleshooting short outs.
DCC is the future, and the future is now. It is an ingenious way of having 2 or more trains running on the same layout, doing different things and even running in different directions. DCC gives you control of each locomotive's speed, direction, sound, smoke, and lighting independent of the others. Every locomotive has a DCC decoder installed on its engine. The DCC unit assigns an address to this decoder so that the locomotive will only respond when the DCC unit sends a message to that decoder's address, and ignores all others. This type of control is great for advanced model railroaders as it allows them to control trains more realistically, and build more complex layouts. And it also appeals to beginners, because they won't get discouraged from dealing with a lot of wires and short outs. You should be warned, DCC-equipped locomotives are more expensive than regular DC locomotives.
Advanced technology comes with a price, but the extra enjoyment, and time gained from not having to deal with wires, is well worth it. If price is an issue at the moment, there are DCC-ready locomotives that can be bought instead. This type of locomotive will allow you to run it as if it were a DC locomotive, but you have the option in the future to buy and install a DCC decoder. It's great for staying within your budget until you can afford the extra expense. I believe once you realize the amount of fun you can have with DCC, you will wonder how people lived without it.