Indefinite Leave to Remain (ILR) is also commonly referred to as 'Permanent Residence'. If you are a foreign national and you are granted Indefinte Leave to Remain, you will have permission to live and work in the UK without restriction.
ILR is often a step toward applying for British citizenship, allowing you to settle in the UK permanently. However, it may lapse if you leave the UK for an extended period, typically two years or more.
You need to provide your valid passport. If you arrived in the UK under a different passport, you will need to prove this too. Any other passports you have held during your time in the UK will need to be provided as well.
A Biometric Residence Permit is a form of identification that many people with leave to remain or further leave to remain have, allowing them to confirm their immigration status while living in the UK.
If you are living in a property which you own or which is owned by yourself and/or your partner, you will need to provide title deeds or a letter from your mortgage provider to verify ownership status.