A git ignore file is just a text file that follows traditional bash file structure.
So if you wanted to ignore the entire current folder you'd type:
./ means current directory
Also if you type
*.jpeg you would ignore any file with the extension .jpeg at the end of it
So if you want to exclude a folder name you'd type a like that looks like this
./<folder name>/a common folder that is excluded is node_modules, because it stores local packages that clutter your workspace, so you'd type
./node_modules/ in your gitignore file.