Correlation and regression mean that there is a certain relationship between variables, but it is not as rigorous as functional relationship. This relationship is correlation, and variables are called correlation.

If the correlation is linear, it is called linear correlation between variables. If there is correlation between variables, it is necessary to study the quantitative relationship between one variable and other variables (or influenced by its variables).

This variable is called dependent variable, and other variables are called independent variables. This quantitative relationship between dependent variable and independent variable is called regression of dependent variable and independent variable. Statistically, the method to study the correlation between variables is called correlation analysis, and the method to study the quantitative relationship between dependent variables and independent variables is called regression analysis.