Please give us more information about your case.
The applicant is the one applying for getting sponsored.
The sponsor is the PR or canadian citizen who sponsors the applicant.
If your mother wants to come to Canada and wants to be sponsored then she is the applicant.
EDIT : Sorry just read that your post doesnt say anything about family class/sponsorship.
If thats not your case then just ignore what I just said about it.
But generally the applicant is the one applying for a visa,work permit etc.