Just about everything you can do with a mouse can be done with a keyboard shortcut. Although most people don't care to learn the shortcuts, they can be handy in various instances (for example, when the mouse fails). Some keyboard shortcuts are also time savers.
Many of us use "Cntrl + C" and "Cntrl + V" to copy and paste, respectively. These are two shortcuts which are not only time savers, but also tend to work in those instances where "Copy/Paste" are not available on a right click of the mouse.
Most software applications also have keyboard shortcuts. For example, if you're typing away in Microsoft Word and want to save your document, you can hit "Cntrl + S" on the keyboard. This same keyboard shortcut works in most other software applications too.
When you're working in software, you can usually figure out the keyboard shortcut by looking at the menu. Commands (like Save, Exit, etc.) will usually have the keyboard shortcut next to it ... they'll have a letter underlined. When you see a letter underlined in the menu, it typically means that hitting "Cntrl" plus that letter on the keyboard is the shortcut.
Here's handy link with some keyboard shortcut cheat sheets you can download. Notice that the shortcuts are divided into categories. If you keep a 3-ring binder next to your computer for notes, printing these cheat sheets out and putting them in it could prove useful in the future.
Like anything else, the more you use the keyboard shortcuts, the more you'll be able to remember them.