Hey Sandeep Panda nice start to gather basic knowledge.
To answer this, let's take the example of master and development branch.
To merge the content of master branch into development branch, we use
git merge development master
or
git checkout development
git merge master
Now, we have a new merge commit in development branch which doesn't alter the history of development branch.
To rebase a branch means moving the base of the branch to a different position, i.e; re-writing the project history by inserting brand new commits.
git checkout development
git rebase master
💡Use merge when you work on a shared branch and use rebase when you are the only one working on the branch. This is because altering the history of a shared branch might introduce conflicts.