I understand the purpose of tanks and carries but why need a support charter. DO i high elo games even use them,cause if you have a tank and a team of carries. What else you need. carries do much more dammage and are way useful in teamfights and need them to win. Are support really necessary.

Depends on how you define support. Taric/Nasus/Soraka are support heroes, and are incredible. Sivir can be considered a support because she isn't a hard carry, and aura stacking on her is ridiculously powerful. So yes, support heroes are great.

Janna. Slow, disable, pushback, heal, shield. Saves the carries from dying, therefore being unable to carry.

4 carries and a Taric will most likely win against 5 carries.
In low elo games, you can pretty much play any champion and carry for the team. Anything near higher-tier mid to high elo will involve a lot of team fights, and support champions change the tides of battle quickly.

Supports can swing the tide of battle in many cases if used correctly, and they cover the many weaknesses tanks and carries have. I find that supports aren't always necessary, but I definitely feel much better with them around since they can help you kill/escape instead of relying on shear damage or armor to dominate. It's like they add a new dimension to a puzzle instead of "go there, attack".

Offtopic: hey OP, I remember having played against you this Saturday. You were Twitch, I was Twitch, good times xD Any luck with Anivia?

And if you think it's creepy that I remember you... yeah I think it's creepy too. Let's just say your name is memorable o.O

Supports provide three important functions:

1) Aura item stacking. Aura items are insanely powerful in high-tier play because they help everyone on your team (and/or hurt everyone on the opposing team), effectively providing 5 times the aura benefit in team fights, which is what high ELO is based on. Anyone can theoretically pick up these items, but there are often better items for various other champions to fulfill their roles properly. Supports, on the other hand, should have first slots dedicated to these items. Having a Taric/Sivir who you know is going to take a Starks + Aegis and a Soraka/Jana who you know will take a Soul Shroud + Abyssal Scepter helps everyone on your team immensely.

2) Healing. Not all supports provide this, but it can be invaluable. When two teams are on the verge of a teamfight, there is a lot of long-range harassment going on. The team capable of staying at full health in the face of this is the one that will be able to come out on top of the eventual teamfight.

3) Buffs. Whether these are AOE buffs like Taric and Sivir or single-target buffs like Jana and Soraka, making your team or carry better gives you a better shot of winning the fight.

Support is very viable and is currently one of the FoTM tactics in higher elo play. Taric + Soraka is very powerful. You will see a lot of teams run with something like Taric, Soraka, Alistar, Sivir and another carry of some sort.

The interesting thing about supports is that they can be the single biggest reason that your team wins without ever getting any kills. In fact, not getting kills actually helps! more kills for item/gold dependent heroes.

This applies even to farming. If you pick hero that doesn't need that much farming, it will mean that your mates can farm better.