If you've spent a significant amount of time looking at jQuery code you've probably run across the following lines of code/function calls:event.stopPropagation() event.preventDefault() return false
I've include a link to a CSS trick guide that does a great job of explaining, in detail, the core differences between the three, and I'll summarize them below.
The default behavior for a link is to navigate the user to the page or section of the page that the link points to. However there are many times in jQuery that you want a link click to perform some other action, such as liking a post, submitting a comment, etc. The preventDefault() function simply stops the default HTML behavior from occurring, so the link click won't take the user anywhere, it will simply run the jQuery code from within the function.
When you return false, jQuery automatically runs both the stopPropagation() and preventDefault() functions.