visual git glossary

local

repository: the entire recorded history of a project, including all of its versions
commit: a recorded set of changes, a version of the repository
parent: the commit another commit is based on, the previous version of a commit
working tree: the current content in your local repository, including changes you made
HEAD points to the commit your working tree is based on
staging area: a location between working tree and HEAD, used to iteratively prepare the next commit
branch: human readable name pointing to a commit, advances when you commit, includes the inheritance of the commit it points to
master: convention for default branch name
tag: human readable name pointing to a commit, without advancing, purpose: give a version a human readable name
merge commit: a commit with two parents

remote: a (usually remote, i.e. somewhere else, as in distributed) copy of the repository that is different from your local repository
origin: convention for naming your publishing remote repository, the one to which you can write/push
upstream: convention for naming the repository of the original author, the one on which you want to base changes on, the one that everyone uses and trusts, the one from which you pull, the one to which you want to send pull/merge requests
fork: when you initially create your origin from upstream
clone: when you just create a local copy of some upstream repository, without intention to contribute, but just to inspect or use
pull/merge request: set of commits you present to upstream (the original author / the community) for review