Peripherals
Peripherals are how we interact with our computers and tech devices.
Generally peripherals are structured into two types, input and output. With input peripherals you give you computer data to work with. Output peripherals on the other hand show you the data your computer wants to show you or you want to have shown.
Sometimes there's also combined devices, but they are generally still able to be split into their individual tasks, a touchscreen for example is a pointing device and a display.
Pointing device
A general device to point at things on a graphical user interface.
Mouse
The most well known pointer for a computer. You move a cursor on a screen by moving the mouse in the x and y axis. Generally the x axis is moving left and right, the y axis is forward and backward. Mice in general have two buttons, Left (LMB) and Right (RMB) mouse click. On most better mice the mouse wheel is also clickable as a third button (MMB). In that regard there is also the mouse wheel with which you can scroll content.
The use of the left click is normally for normal interaction with content, this includes following links like this, applications and so on. The right click is normally for context menus. For example when you right click on an image on this page you'd see a menu like "Open image in new tab", "Save image as" and so on. To use one of those menu items you'd use the LMB again. The Middle button is normally used to replace scrolling with the wheel, and instead use the position of the cursor on the screen. Most operating systems allow you to swap the jobs of the LMB and the RMB, where now the right is the main button and the left is the context button. This feature is mostly intended for people having the mouse on the left of the keyboard, for example left handed or ambidextrous people, but it can also be uses as an accessibility feature. The mouse wheel, also called scroll wheel, is used to scroll vertically in many different use cases, on the web it is normally used to go up and down on a page. Sometimes the scroll wheel can also be tilted left and right to scroll horizontally.
For gaming there's special mic with high DPI, fast polling rates and other such features. These mice also often include additional assignable buttons aside from the regular Left and Right buttons. In games you can often set what you want to do with which button, including the MMB. For creative work there's sometimes mice with a second scroll wheel, which is assignable. For both of these you can often assign the function of every single button, including the primary buttons.