Well i can just tell you a little bit if it that i know about recruitment process. Well their are many recruitment process outsourcing companies that deals with recruitment of many clients. They basically have tie-ups with clients and they tell them about their desired requirement and the recruitment firm having expertise in recruitment and recruiters search for the deserving candidate through their database and follow the desired quality checks like screening etc. If they find it suitable they than forward it to the client for further processing like face to face interview etc.

You can get more information on the internet or you can browse through Recruitment Process Outsourcing