Point-and-click is the action of moving the mouse to a specific location and clicking an object to perform a specific task. For example, when you click on any hyperlink on a web page you are moving the mouse to point at that link and then clicking the link to open the page.
When describing a computer or online game, a point-and-click game is any game that involves the user to find and click on different portions of the screen to unlock and discover new things. For example, in a point-and-click game, you may see a picture of a scene and have to find a key that can be used to unlock a door. Myst and Riven are two perfect examples of early point-and-click games. Today, there are hundreds of online point-and-click games available done using Adobe Flash and HTML5.