Different types of ratings?

I'm new to chess, started playing around mid-December and now I'm confused about something, so basically my rating is like 550 and in a rapid game I get no mistakes, blunders, or missed wins usually, but on youtube, I see 1200's worse than me, and I came across a video today by GothamChess, on the thumbnail it said something like "700 game, 19 blunders". It sounds like these ratings are tripled. I just googled "starter rating on chess.com" and it said 1200, I started on 400. Can anyone help me to understand this?

Say you play a fried liver and you win, you usually get no mistakes because the game ends in the opening. When people like that 1200 play, the play average with mistakes and whatnot, and that 700 with 19 blunders is probably a troll account or wasn’t even trying. 

The answer to your 2nd question is you choose what rating you join from.If you choose new to chess,all your ratings start with 400, and the list goes like 

Beginner: 800

Intermediate : 1200

Advanced : 1600

mMaster : 2000 

Does this help or do you still have any questions?

"When people like that 1200 play, the play average with mistakes and whatnot"

Don't understand this.

In any game, you will always see a mistake, sometimes you will have no mistakes if you played a great game, but your average chess came will have mistakes.

The initial ratings granted to each individual new account vary depending on the starting options selected. Some start out as 1200...some 2000...some 400...and then there are others as well.

That, of course, does not necessarily mean that a 1200 rated player is necessarily stronger than a 400 rated player - this temporary rating is there because the site does not recognise your true strength until you have played sufficient games. The site takes your starting options as "true".

Don't worry about rating.

Even 2000s blunder their queens sometimes.

It is easier to blunder playing against a stronger opponent than against a weaker opponent, since stronger opponents tend to make better moves. Example, if I play some 800 I will have much less blunders than if I face a master.

You start at 400 because you chose the option "new to chess" but the first few games rating varies by the 100s until it can accurately place you in your actual rating strength.