Hi jnathan, thanks.
If there is interview it could be for any or some of the following:
1.to ensure the accuracy of the information contained in the documentation submitted;
2.to clarify issues relating to his background; .
3.to confirm whether he/she possesses the necessary means to settle in Canada;
4.to verify the absence of security in-admissibilities;
5.to ensure the applicant is intending to enter the Canadian labour market;
6.to verify whether there are sufficient grounds to exercise positive discretion; etc. or

coud be possibly anything that is not mentioned here