While creating a Workflow, you can create process steps and add multiple tasks within a step. When tasks within a step are completed, the workflow moves on to the next step. A step can be assigned to a user or group of users. All members of group will be responsible for that step but only one person within the group can take ownership of a step.
Every time a step is completed and the work flow moves to the next step, an email notification is sent to user/group responsible for it.