What is the difference between git pull and git reset --hard origin/<branch>?

$ git pull                        
# takes the latest changes of origin/branch (exists both local & remote changes)

$ git reset --hard origin/branch  
# replace your local with origin's branch history (discard local changes)

Example: Say, we have two commits in local A, B and remote has two commits A, C. Now if you pull then your local contains A, B, C unlike if reset then your local will have A, C not B.

The following commands:

git fetch
git reset --hard origin/<branch>

will discard all local changes.

Where as:

git pull

Which is exactly the same as:

git fetch
git merge origin/<branch>

will attempt to preserve local changes.