Linear interpolation uses two points and assumes the third point lies on a straight line in between them

Linear interpolation uses two points and assumes the third point lies on a straight line in between them. A line of best fit uses most of the points to approximate the likely position of other points.

Linear interpolation can be performed by joining 2 points on a graph with a straight line. A line of best fit is different, as it doesn't necessarily go through any points.

Which technique is best to use depends on the situation. If you have access to the graph, drawing a line of best fit and using it to estimate the value of a new point is quick and easy to do. Without the graph, linear interpolation allows us to just take the coordinates of 2 points and come up with an estimate for a new point.

However, linear interpolation assumes that there is a linear relationship, which might not be true! If you see a graph with a curved line of best fit, linear interpolation would not give an accurate answer here!