In reality it is normally based on seniority, assuming internal requirements and government standards are fulfilled. Ie; to be an airline captain you require, amongst other things, at least 1500 hours to qualify for an ATPL licence. However most companies have higher requirements than this to be considered for captaincy, and in most cases seniority list dictate the rest. That means you could have a truckload of experience, but if the company already have enough captains (normally a bit over half the corps), they will not upgrade you until there are vacancies anyway.
The different types of copilots, for those who have it, may be based on number of hours or time of service. Not airlines have these subcategories. However, upon entry into service the pilot would normally do "line training" with experienced captains. This is to prevent an inexperienced copilot to fly with a (relatively) inexperienced captain. Following this period, which could last a few weeks to a few months, you would be "released" into normal line ops with "any" captain.