Regression is used to determine how one dependent variable is related to one or more independent variables.
Dependant variables change as the independent variables change. Usually, the independent variable is shown on the horizontal x-axis and the dependent variable is shown on the vertical y-axis.
For example, you could use a regression analysis to determine the relationship between the age of a car and how far it has driven. You could use the regression fit to understand how mileage changes with car age, or predict how far the car will be driven in the next year.
When To Use Regression
Regression is a useful tool for understanding relationships between variables and forecasting.
If you understand the relationship between an independent and dependent variable then you can make changes to the independent variable to influence the dependent variable. If you understand how the independent variable will change with time, then you can use the regression fit to forecast the value of the dependant variable over time.