The person who buys a piece of land is known as a freeholder. This title confers complete ownership of the land and the buildings on it until they either sell the land on or leave it to someone else when they die.
Many people buy individual flats that are part of a purpose-built block. They will normally hold a lease for a certain period of time. They are allowed to occupy the flat during that time. They can sell the lease on the flat within that time period and pass on the remainder of the time to the new leaseholder.
For example:
A flat is bought on a leasehold in 1999. The term of the lease was 99 years when originally granted in 1955. In 1999 the outstanding term was 55 years.
A person in this position are usually regarded as owning the property outright. In reality they are in a similar legal position to a weekly tenant in the sense that they pay a ground rent and service charges to a higher landlord (the freeholder) for maintenance, services, insurance and management of the whole building (which includes their flat) and are the leaseholder of the freeholder are bound by the terms of the lease.
If the leaseholder then lets out the...