It is a short form of have got to.

Gotta is a way of writing got to that shows how these words are pronounced in the expression have got to in casual speech: have gotta. 

Have gotta is an informal way of saying that something is necessary or must be true.

In very informal language, gotta is sometimes written and spoken without have.

Examples:

• I gotta go now.
• He’s gotta be kidding.
• I gotta go now.=I have to go now.
• Gotta ciggie?=Have you got a cigarette?

The Got to Meaning in English

The gotta has been a staple of English speaking nations around the world for centuries. Its usage has evolved from its early days as a slapped on for good luck to a no-nonsense word of mouth. As a result, there is no shortage of merriment and snark in its wake. And while many of us are prone to blatant self-promotion, it is often the case that someone might actually want to hear your spiel. So, how do you make that happen?

First, you must be clear on what a gotta is and what a gotta entails. Second, you need to know where and when you’re going to use it. This is a bit trickier than you might think, especially if you’re a nerd with a penchant for esoteric pursuits. Once you’ve nailed the gist of the gotta, you can then proceed to the next step. Aside from learning what your gotta is, how it is used and when it is used, you will also learn the pitfalls to avoid. If you’re looking to improve your gotta game, you’re going to have to make some tough decisions.