The plot is what actually happens: the storyline.

The sequence of events in the plot is the foundation (basis) for the story to unfold and is meant to organize information and events in a logical manner.

The plot of the play is the main point of a play. Each character contributes to the plot of the play.

the plot

Not necessarily. The plot is the main storyline. For example if a books character needed to defeat an evil enemy but at one point had to do training with an unknown teacher it would be a kind of 'side story' although it does weave in with the main plot. Or the story might switch from the main character to another characters point of view so that you could see what they were doing. Again this will probably weave in with the main plot but it is still not the main plot.

A subplot is a part of the narrative that is separate from the main plot of the story. It is a side story that usually related to the main plot but are not as important to the work.