Dear firend,
first about visa--it is a entry clearence to enter country,There are many catagaries of visa and each shows the purpose of entry.
-and resident permit is permit to stay in country in accordence of your entry visa.Your visa you may have to use within 3 to 6 months from date of issue and it may for single entry and maximum stay 1 month.But resi permit may be given from 1 year up to five years(specially family of Qataries).you can go and come back as much you like with r.p.
Your next que., to make your entry visa it need pp copy only if your employer is person but in case of company you may need contract, in some case police clearence certi also.