We email reminders before expiry and, with auto-renewal on, issue the invoice in advance.
If the domain expires:
- Grace period (about 30 days): site and email stop working, but you can renew at the normal price.
- Redemption period (about 30 days): it can be recovered for an extra registry fee.
- After that the domain is released and anyone can register it.
To stay safe, register your domain for several years and keep auto-renewal on.