Asset class = a broad category of investments (stocks, bonds, cash, inflation-protected securities)
Thinking about broad asset classes before you think about choosing investments is a great way to simplify investing. It's like looking at a forest and focusing on the different types of trees, instead of each leaf on each tree. One simple way to practice asset allocation would be to invest money in equal amounts among each asset class. Of course, there are many different ways to split up your money - and some are much better than others.