what is the difference

[balakrishnanijk]

Given below are three sentences:
1.He works in a company.
2.He works on a company.
3.He works for a company.
4.He works at a company.
Are all these sentences correct?
If not, why?

[Casiopea]

1. He works in a company.
=> The emphasis is on works, the action, what he does in the company.

2. He works on a company.

3. He works for a company.
=> As opposed to, say, works for himself.

4. He works at a company.
=> The emphasis is on a company, the place, location.

Does that help?