Standard vs. non-standard endorsements
Standard endorsements refer to really common things people often change on their insurance policy (e.g. change of address or adding extra coverage for sewer backups). They’re kind of like templates, but for updates to your policy.
Non-standard endorsements either change these “templates” in some way, or come up with something new altogether.
Mandatory vs. voluntary endorsements
Mandatory endorsements are relatively rare, and refer to something that’s required. Read: there’s a law in your state requiring this change to your policy.
Voluntary endorsements are (as you may have guessed) not required – these are the most common types of endorsements you’ll encounter.