Indefinite Leave to Remain
When you have been granted Indefinite Leave to Remain, it means that there is no longer a time limit on how long you can stay in the UK. You are free to come and go as long as you wish. You will be issued a Biometric Residence Permit Card.
The BRP card will have an expiry date, lasting 10yrs, so you will need to apply for a new card [at least 3months] before it expires.
You also need to keep the information on the card up-to-date so if you need to change your name or address for example you will need to tell the Home Office.