There are 10 levels of approvers. Each level supersedes the next so a level 1 approver will need approval from a level 2 approver. Only one person of a specific level needs to approve an order, so for level 1 if you have two approvals only one of them needs to approve the job.
Requesting approvals will send notification and can be denied or approved from the links within those emails. Additionally, you are able to manage approvals from the site itself.
Below is a list of possible statuses you may see in the approval status window.