A person who has received a British permanent residence permit (ILR) can stay in the UK without any restrictions: they have the right to live and work in the country, regardless of how long they stay in it. Upon all immigration requirements compliance, the holder of permanent residence has the right to apply for British citizenship after 12 months.
Receiving permanent residence permit involve permanent residence in this country for a fixed period of time: as a rule, you have to live in the UK for 5 years a row (in some cases, the required period of stay may be shorter). Permanent residence applicant must meet all immigration requirements that are applied for valid visas holders.
Permanent residence means that a person has been living in the UK for 180 days in a row within any 12 months comprising the reporting period.