The team who loans a player from another team doesn't own them, but they usually pay his wages. Often teams will loan out players who are too young/inexperienced to play for their main team, since they can gain experience and they don't have to pay their wages.
If Team A sign a player, but he's too young/inexperienced to play for them, they will often him out to other teams on loan. So say they loan him out to Team B, this means Team A still own the rights to him, but while he's on loan, they don't have to pay the wages because Team B will pay the wages.
Although, the case of Torres is a little different. Torres was on loan from Chelsea since the start of the season, however in the mid-season transfer window, Milan got Torres on a free transfer deal, so Milan are now the owners of him. As soon as the deal was completed, they loaned Torres to Atletico Madrid, in exchange for Alessio Cerci.
Unusually in this situation however, instead of Milan paying the wages of...