The slopes and areas of of the three kinematics graphs (x vs. t, v vs. t, and a vs. t) have meanings which are important to understand. The following links take you to explanations of these meanings.
The slopes have meanings, click these links to read more:
Slope of the x vs. t graph is velocity.
Slope of the v vs. t graph is acceleration.
The areas have meanings, click these links to read more:
Area of the v vs. t graph is change in position.
Area of the a vs. t graph is change in velocity.
Summary: