Joining the points if we get a straight line, that graph is called [[1]]

Line graph - Line graphs are used to track changes over short and long periods of time.

Bar graph - Bar graphs are used to compare things between different groups or to track changes over time. 

Pie chart - A Pie Chart is a special chart that uses pie slices to show relative sizes of data.

Hence, On joining the points if we get a straight line, that graph is called a line graph.