Terminal git:master after oh-my-zshell installation
Typically some of the oh-my-zsh themes provide special prompts for directories that are Git repositories. The 'git master' just means that it thinks that the directory you're in right now is a Git repository, with new, unstaged changes. All of this has to do with source control. I don't know your background with source control but you can look it up if you're curious.

I would start with looking at your ~/.zshrc file and see what ZSH_THEME is set to. Then, I would look inside ~/.oh-my-zsh/themes/ and look for the theme that's set in ~/.zshrc. This latter typically has the prompt set that you're seeing right now. After this I'd change the prompt to look the way you want. In your case you might just want to disable the Git-related stuff from the place where the prompt is setting those variables.

Good luck!