The intercept is the point at which the regression line through the non-null data pairs in the sample intersects the ordinate, or y-axis, of the graph.
The plot of the linear regression on the variables is used to predict the behavior of the dependent variable from the change in the independent variable.
Note that this computation assumes a linear relationship between the variables.
There can be a strong nonlinear relationship between independent and dependent variables, and the computation of the simple linear regression between such variable pairs does not reflect such a relationship.