It’s a little device sitting next to your computer or it’s one you bought to use with your laptop. Usually wireless (it talks to the computer via radio or Bluetooth) and has a laser in the bottom for tracking. Basic mice have two buttons and a scroll wheel. The buttons are the left and right buttons. The left button is used to select an item, such as an icon, file or folder (but not limited to). For Windows 7, the icons on the Taskbar along the bottom of the screen can be activated by one click. This is called a single-click. Icons on the Desktop can be activated by two clicks in quick succession. This is called a double-click. You can also use the left button to click and hold on an object (such as an icon on the desktop), then move to where you want it to be. This way, you can organize your desktop by putting like programs together.
Left clicking is for when you want to select or activate an item. Single is usually for selecting (unless the icon is on the Taskbar). Double-click activates an icon to run the program or file by opening the associated program.
Right-click gives you options for what else can be done with an icon, program or item. The menu changes depending on where you right-click at. For example, if you right-click on the Desktop, the menu is different than if you right-click on a folder or file. Some option include Open, Explore, Properties, New (for document creation), and other options. The options will change depending on where the right-click is done and will pertain more to where the right-click is done, such that a right-click on the Desktop will show a different menu than right-click in folder or on an icon.
Knowing the difference between left and right-click and knowing where each is appropriate will make your computer experience more positive and help you to be more productive.
An example of the menu that results from right-clicking on the Desktop.