The context menu is a pop-up of options in any program that changes depending on what the mouse is pointing at when you open it. It is accessed by right-clicking on an object or area. The context menu (sometimes called the shortcut or pop-up menu) reveals options for whatever the mouse is pointing at. For example, when you right-click on a misspelled word in MS Word, the context menu that pops up presents options for addressing the misspelling.
If your mouse doesn’t have a right button, hold down the ctrl key when you click or click with two fingers (the latter is a gestures option you may have to turn on in your computer’s settings).
As Learning Tool
Because they show functions associated with an item (or even a blank area), context menus can help you learn what a program can do, or how you might interact with various on-screen items.
Right-click on a tracked change and the context menu will show you options to accept or reject the change, toggle Track Change on or off, and a few other functions. Right-click on a graphic and you’ll find out that there are alignment options and that Word lets you enter the alt text that will be read by screen readers, making your documents more accessible.
Right-click on a file in a finder window and you’ll find shortcuts for organizing, renaming, and viewing the files, among others.
In WordPress, right-clicking in the body field of a post editor will give you access to emoji and symbols.
As Productivity Tool
Because they show you the most common functions associated with an item, context menus can speed up your work. It means fewer clicks, and no hunting for the right ribbon to find the tool you want.
Some features may only be available via the context menu, in some programs. Looking up synonyms is what I use the context menu for most often in Word.