The plot is the path a story takes to get from the beginning to the end. The path can be straightforward or convoluted, but in order to work it must get the characters from point A to point B by means of logical cause and effect, much like a string of dominoes. If there are pieces missing, positioned badly, or stuck in where they shouldn't be, the whole thing can fail.
Plot is one of the key elements that makes a story either good or bad. A plot that is intricate and plausible without being predictable is generally a good plot. A plot that is boring, cliché, and full of holes is a bad plot. Having no plot at all is also considered to be very bad.