a person send his resume to a company

A resume is not an offer. An application can be an offer. A call for interview is not a counter offer or acceptance.

so what is this ???

sending CV to companies

call for interviews

getting  job letter 

A call for interview is to assess whehter the candidate will be suitable for the position, which the compnany may have. If at the interview the committee that interviews finds the candidate is suitable, they may givehim/send him job letter. The job letter is an offer of placement.