this is your Work visa. You can use it for entry to Qatar only once. After that your Residence Permit must be issued without leaving Qatar.
Work visa is always given for 5 years (with the exception, when WV is issued for 2 years only).
Once you are in Qatar, your company will process your Residence permit, initially for 1 year (sometimes for 2 or maximum 3 years).
Your RP is renewable within these 5 years. Once 5 years are gone, to renew your RP they wil have to go again through the Labour Departent as if they issue new WV for you.
Anyway, don't worry. everything is all right.