Generally these are the weaker supports who have spell bursts and a poke and/or some control like an AD carry. This type of support is very good when accompanied in the early game by a powerful AP carry with some burst. Note that these supports often require some skill because a bad early could put you very behind.
These champions are generally balanced and effective in either offence or defence. They sometimes have a heal, a shield or even some poke or control. Often they are powerful in the late game for teamfights and hold the lane very well while playing passively. They can be played in either an offensive or defensive team composition.
These are the champions who can protect your AD carry in the lane and tank a huge amount of damage in a teamfight. They are often picked as a safe choice because even if they won't be able to take the advantage in the lane, or might even lose it, they are always useful in the game! In the lane these champions are extremely powerful because they often have controls and can tank a huge amount of the damage from then enemy AD Carry!