Linear regression is a statistical method used to model the relationship between a dependent variable and one or more independent variables. It aims to find the best-fitting straight line that predicts the dependent variable based on the values of the independent variables. This line is determined by minimizing the differences between the observed values and the values predicted by the model. In a simple linear regression, there is one independent variable, while multiple linear regression involves two or more independent variables. The output of a linear regression analysis includes coefficients that indicate the strength and direction of the relationship, helping to make predictions and understand trends in data.