When a record reaches a certain workflow stage and is assigned to you, while you would ordinarily process it yourself, you can also forward your assignment onto one or more other users or roles.

You do this using the Assign action, which you will find on the Whats Next list, when you're viewing the record:

Clicking this will bring up the assign form:

When you assign a workflow record that is assigned to you, that person will take over the workflow action for you and you will no longer be able to act on it.

Note, though, that the person you forward the workflow to must have the roles required to run that action. If you forward it to someone who does not have the required role, they will not be able to complete the action and will have to forward it to someone who does.

Also, if you forward it to multiple people, the first person who responds will be the one that determines the outcome. After the first response, all other assignments for that workflow stage will be removed.