Your contract with a landlord will probably be what is called an 'assured shorthold tenancy', or AST. ASTs go back quite a way – they were introduced with the Housing Act 1988 and revised with the housing Act 1996.
An AST usually lasts for six months – but can be longer. ASTs provide protection to tenants against eviction, unless the tenant breaches their responsibilities under the contract. A tenant may still be evicted if, for example, they fail to pay their rent – but due legal process must be followed.