Examine random access memory
Processing all those ones and zeros can take up a lot of brain power. Even the mighty GPU is limited in how much work it can do. In order to solve this problem, computer scientists created something called random access memory, or RAM for short. RAM was invented to store chunks of data that the CPU can grab and use when it needs it and temporarily store it when it doesn't.
Think of it like your own short-term memory. Say you're talking with someone. As you're talking, you remember three things you want to say. When it's your turn, you remember the first item on your list and "store" the other two for use later. As you speak, you may then move on from the first topic (but hold on to it so you can come back to it later). You then talk about the second topic (or third if you want to skip around). You may go back to each of those topics over the course of your conversation but you're only talking about one at a time.
Random access memory works similarly. The CPU can think about only certain data at a time, so it keeps the rest in memory until it needs it. It's referred to as "random" because the CPU can think about anything stored in memory anytime it wants.
RAM on a computer tends to be fast. But it also can cost significant money relative to the other parts in the computer. However, when buying a computer, it's generally a good idea to get as much as you can afford especially when you tend to work on large files like drawings.