You can create either first, and make the association at any time. Once associated, searching either for contact or company, using the search function in the main menu, will very quickly bring up the right results.
A company is an account, or an organisation, that you might do business with. A contact is a person at that company.
Companies and contacts have different defualt properties reflecting the different types of entity they represent. Also, multiple contacts can be assocaited with one Company.
Is there anything more specific you would like to know?
You can create either first, and make the association at any time. Once associated, searching either for contact or company, using the search function in the main menu, will very quickly bring up the right results.