The word, "ain't" is a contraction of the verb "to not be." It is used in colloquial english and is generally viewed as a slang word that is not meant to be used in formal writing.
The term LOL Is frequently used in chat. LOL stands for "laugh out loud." People use this term when they are chatting or exchanging emails to explain that they are laughing loud enough so that someone would be able to hear them. They might use this instead of "hehe" which would mean a more quiet laugh or a giggle.
The word, "gonna", is an informal conjugation of the verb "to go." When we say "gonna", we don't mean "to go" in the sense that we are moving from one spot to another. Instead, "gonna" is an abbreviation of the words "going to" when we are using the "verb", to be going to . "To be going to" is used to express that an action is going to occur in the future.