Line graphs
In a nutshell
Line graphs are a visual way to show changes to a measurement over time.
Example 1
This line graph shows the change in temperature of an icy glass of of water left in the sun.
Temperature of water left in the sun over time
Interpreting line graphs
Line graphs have the thing being measured on the $y$axis and the time on the $x$axis. To read the example above, pick a point and move down to see the time, or across to see the temperature.
Tip: Remember the $y$axis is the vertical one (side) and the $x$axis is the horizontal one (bottom).
Example 2
In the above line graph, after $6$ minutes the temperature is $8\degree C$.
Drawing line graphs
Drawing a line graph is very simple:
PROCEDURE
1.  Draw and label the axes.

2.
 Plot each individual point on the graph using a cross. 
3.
 Join each point together with a line. 