Here you can find a short and partial recap table, where I try to pair the most common Subversion and Git commands to help Subversion users to quickly shift their minds from Subversion to Git.
Remember: in Subversion tags and branches represents physical copies of a source branch (the trunk, another branch or another tag), while in Git a tag is only a pointer to a particular commit.
Merging
(assuming the branch was created in revision 42 and you are inside a working copy of trunk)