Residual plots are used to look for underlying patterns in the residuals that may mean that the model has a problem.When using the plot() function, the first plot is the Residuals vs Fitted plot and gives an indication if there are non-linear patterns. For a correct linear regression, the data needs to be linear so this will test if that condition is met.
Residuals should be normally distributed and the Q-Q Plot will show this. If residuals follow close to a straight line on this plot, it is a good indication they are normally distributed. For our model, the Q-Q plot shows pretty good alignment to the the line with a few points at the top slightly offset. Probably not significant and a reasonable alignment.
