User blog comment:Fistful of Force/Bot lane supports/@comment-5514182-20131202013539

You said it right. There's a difference between having a dedicated support or a mage come out of the laning phase. Supports will focus on PROTECTING the Carry, becoming an extension of the ADC, while Mages will focus on DEALING DAMAGE, becoming an independent factor in fights.

You still have to factor in what the team needs as well. If you lack initiation Annie, Sona, Thresh, and Alistar are 4 examples of common supports will initiations. They are not the same, however. Annie has strong damage and targeted CC at a range. Sona can sustain and poke in lane. Thresh has his lantern and his hook. Alistar is exellent at peeling and tanking.