It is a kind of agreement used in terms of tenancy reference that grants exclusive possession of the property to the occupier where the tenancy can be determined immediately by either of the party.
It may involve verbally agreed tenancy reference; at the same time, it can be brought to end at any time by either party.
In such a condition, the tenant has the permission to live in the house but may not have a lease or a formal UK real estate contract that specifies the length of tenancy.
Such agreements are sometimes called at-will agreement and are often created before becoming a landlord. The agreement can be modified into a documented contract at a later stage.
In the absence of any written agreement, both parties are provided legal protection and they have certain legal obligations like the landlord should provide a safe environment to the tenant as per the law and they need to provide a notice when the tenancy starts.
The tenant has the responsibility to pay rents and avoid any kind of wear or tear to the property.