A lease is a contract between the leaseholder and the landlord giving conditional ownership of a property typically for 99, 125 or 999 years. The lease sets out the contractual obligations of the parties. The leaseholder's obligations include the payment of ground rent and contribution to the costs of maintaining the structure, exterior and common areas of the property.
Like every other leaseholder, you own the lease - the proof of your right to live in the property. Do not lose this lease, it is a legal document. If you do lose it you can obtai a copy from the Land Registry.
Each lease is drawn up for the first leaseholder. It contains an agreement between Yarlington and the leaseholder on the premium (price) paid for the property and explaining who is responsible for the property's management.