What is the difference between lobha et rāga ?
In a psychological (and early Buddhist) context, the word rāga means any feeling or passion, (especially) love, affection or sympathy for, vehement desire of, interest or joy or delight in (locative case or compound) etc. (From: Monier Williams Dictionary).
In a secondary sense it is also used in the sense of an inflammation of the above emotions.
It is normally used in a negative context in early-Buddhism - i.e. as something undesirable to have. But it is used in a positive sense too in non-Buddhist literature.
Apart from this there are some other meanings (many of which are from non-Buddhist sources).