There are options at multiple points for emails to be sent out throughout the approval process. Each email will typically include information about what the submission is, who submitted / approved it, any submitter / approver notes, and a direct link to the record where they can then make a decision.

Here is the full list of emails:

Notification to approver
This will send an email to the approver with a request to approve a submission. This gets sent immediately when an submission is submitted, this also gets sent to the next approver when any individual approval is completed and handed to the next approver.

Submission approved / rejected
When the final decision is made on the submission, the originator will be sent an email to notify them of the final decision made on the record.

Submission endorsed - optional, 'off' by default
On submissions where there are multiple approvals there is an option to have the submitter notified on each endorsement / approval along the process. This can create a lot of emails if there are many approvers involved in the process and so it is 'off' by default.