What is mystery shopping jobs?

There are several companies in India which provide mystery shopping assignments. I myself is registered with 3-4 companies. Out of which I really like working with Bare and Trans MR. I have done some great assignments with both of them. I used to do it as a part time work after coming home from a 9-5 job. My frequency was a little less in the earlier time. But as I got to know the skills and I am much more confident now, I love doing mystery assignments. I usually take up more assignments from Trans MR as they have audits in bulk. Their staff provide proper training prior the visit. They even provide a feedback post visit so that you can improvise in your further visits. Also, the payment cycle is fair as I get my payments regularly from them. I rarely have to follow up with them. I have also done some assignments for HS Brands, they too provide a fair deal of assignments.