Fetch
The operation to make your Git aware of the changes in the remote repository.
Example
Imagine you have 1 local repository with 1 remote repository, referenced as origin.
Both the local repository contains the "Initial commit" in the [master] branch.
o "Initial commit" [master][origin/master]    o "Initial commit" [master]
(local)                                       (origin)
Then, some other collaborator updates the remote repository:
o "Initial commit" [master]                    o "Initial commit" [master]
(local)                                        (origin)
What? What change?
If you would like to see the change, you first need to make your Git aware of changes in the remote repository.
How to do it?
Fetch!
                                               o "New feature 1"  [feature1]
                                               |
o "Initial commit" [master][origin/master]     o "Initial commit" [master]
(local)                                        (origin)
Once you do this, you have an idea about what was the state of the remote repository at the time of fetch:
Please note fetching does not update your local repository with the remote changes. You have to pull to sync!