Response variables are also known as dependent variables, y-variables, and outcome variables. Typically, you want to determine whether changes in the predictors are associated with changes in the response.
For example, in a plant growth study, the response variable is the amount of growth that occurs during the study. The investigators want to determine how changes in the predictors are associated with changes in plant growth. The predictors are the amount of fertilizer applied, the soil moisture, and the amount of sunlight.