Here is the meaning of the "Line of Best Fit" refers to a line through a scatter plot of data points that best expresses the relationship between those points. A straight line will result from a simple linear regression analysis of two or more independent variables.
Here is the rule for the "Line of Best Fit"
A line of best fit can only be drawn if there is strong positive or negative correlation. The line of best fit does not have to go through the origin. The line of best fit shows the trend, but it is only approximate and any readings taken from it will be estimations.