What is the difference between sourcing and screening a resume

Sourcing means - from where and how you will find the relevant profiles (candidates). Some of the popular modes of resume sourcing are - Job Portals (Naukri, Monster, TimesJobs, Shine Jobs, Indeed, Dice, etc), Social Media (LinkedIn, Facebook, Forums, Twitter, etc.), References and Professional Networks.

Screening means - validating candidate profile against the given requirement by the internal or external client. So, it's like, validating the experience of the candidate (if the requirement is of 7-10 years of experience, you can select a profile with 5 or 15 years of experience), validating the location of the candidate (if the client want local candidates, you can recommend profiles from other cities), validating the education of the candidate (many companies are specific about the qualification, like, CA, MBA, B.Tech, etc) and validating the industry of the candidate (If the requirement is about an Account Manager in Advertisement industry then the Account Manager from other industries automatically disqualifies). Likewise, there are various other validations one needs to perform in the Resume Screening Process before sharing the profile with a client.