1. You will use that visa to enter Qatar / to visit Qatar. Once you are in Qatar that is the time your employer will process your residence/work permit usually valid for 2 years but it can be renewed. You can request from your employer to have multiple exit permit (so you can can enter/exit Qatar as you wish). Sometimes the company will give you an exit permit (not the multiple exit)so you can have vacation in Philippines.
2. In the immigration you have to show your Qatar Embassy Authenticated Visa (naka attach sa passport mo to), Overseas Employment Certificate (OEC) from POEA (parang resibo lang to kabayan).

Qatar embassy authentication process: Print the VISA from MOI then go to DHL and ask for the requirement for the authentication of your visa. For the OEC go to POEA( sa Ortigas) to know the requirements.

3. You have to go to POEA! you cant leave the country without the OEC. You need the copy of your contract from your employer this is one of the requirements for your OEC (This is the one that delayed my processing of OEC). Tell your employer to send a copy of your contract for you to accept their terms/conditions. (It is actually impossible to perfect a contract while the two parties are in different countries).