Tier refers to how difficult/prestigious it is to get a job in the company. First tier companies choose each individual very carefully and can generally hire an

Tier refers to how difficult/prestigious it is to get a job in the company. First tier companies choose each individual very carefully and can generally hire anyone they want, second tier companies allow some dead wood here and there, but still put a lot of effort to find talent (aggressive hunting, H1Bs, etc). Third tier companies just hire whoever they can afford having their hiring process fail a lot halfway through due to inadequate pay/benefits/conditions and very rarely sponsor H1B for anyone. There are studies that use similar (although not the same) classification.