Just like humans, computers rely a lot on memory. They need to process and store data, just like we do. However, computers store data in digital format, which means the information can always be called up exactly the way it was stored. Also, unlike our memory, the computer's memory doesn't get worse over time.
While memory can refer to any medium of data storage, it usually refers to RAM, or random access memory. When your computer boots up, it loads the operating system into its memory, or RAM. This allows your computer to access system functions, such as handling mouse clicks and keystrokes, since the event handlers are all loaded into RAM. Whenever you open a program, the interface and functions used by that program are also loaded into RAM.
RAM is a very high-speed type of memory, which makes it ideal for storing active programs and system processes. It is different than hard disk space in that RAM is made up of physical memory chips, while hard disks are magnetic disks that spin inside a hard drive. Accessing RAM is much faster than accessing the hard disk because RAM access is based on electric charges, while the hard drive needs to seek to the correct part of the disk before accessing data. However, all the information stored in RAM is erased when the computer's power is turned off. The hard disk, on the other hand, stores data magnetically without requiring any electrical power. For more information on the difference between RAM and hard disk space, view this Help Center article.
Another common type of memory is flash memory, which is typically used for small devices such as digital cameras, USB keychain drives, and portable music players like the iPod nano. This kind of memory, known as "electrically erasable programmable read-only memory" (EEPROM), is convenient for portable devices, since it stores information even when its power source is turned off, but is smaller and more resilient than a hard drive.
To summarize, memory is a vital part of the way computers and many electronic devices function. While memory and RAM can often be used synonymously, it is good to know about other types of memory as well. Hopefully you will be able to store the information you've learned in your own memory.