"Gotta" is short/slang/informal way of saying "got to". ex: I gotta (got to) get up and go to work. Some people do the same with "should have", they pronounce it as "shoulda". ex: I shoulda went to sleep earlier. It isn't proper to write in that form of course but sometimes it is pronounced that way. *Get (or any variation, ie: got) can be used a number of ways. mostly talking about when you are receiving something or reaching a certain place. ex: I am going to get a sandwich for lunch (receive) I got my letter in the mail yesterday. She is going to get back from Brazil next week. understand?

Get is one of the trickiest verbs in English if you ask me, a non-native English speaker. Why? Because depending on the preposition that follows it has different meaning. Study this link (http://www.oxfordlearnersdictionaries.com/definition/english/get). It has 27 (!!!) definitions PLUS study phrasal verbs. Don't try to learn them all at once of course. Beginners first learn this word in 'get up' (wake up) and 'get to the airport' (go to the airport). Elementary students learn how to use this verb to speak about changing situations: It's getting cold. The days are getting shorter in winder.

"Get" in used in a very large number of phrasal verbs and expression, certainly over 100. These just have to be learned as you encounter them. "Gotta" is the way "got to" can sound when pronounced. It is never written this way, except in the most informal cases. As a learner, you should always spell it as "got to".

gotta means got to , like gonne which means going to