With reference to research methodology, a model is a simplified statement that a researcher makes. He or she makes such a statement to try to explain what independent variables are important in determining the value of some dependent variable.
In the real world, the number of independent variables is huge. There is no way a researcher could study the impacts of all of them. Therefore, researchers must hypothesize as to which independent variables are most important to the dependent variable they are studying.
The researchers then make a model by predicting how these independent variables will affect the dependent variable.