Git has a concept called as tree-ish it means something that is part of tree or reference to tree. Tree in git means nothing but the structure of commits. These commits contains the information like Sha-1, date, author, comments and changes.

We are able reference our commit by using full or shorten SHA-1 hash, ancestry or HEAD pointer.

for e.g.:- this will point to the tip of the current checkedout branch i.e. HEAD

 git ls-tree HEAD 

This returns list of files at that point. May also use branch name instea of HEAD.

git ls-tree master

Also can see particular dirctory within the branch

 git ls-tree master directoryname