If you rent your home from a private landlord (and you do not live with your landlord or a member of their family), and your tenancy began after 1997 then you are likely to be an Assured Shorthold Tenant.
This form of tenancy was created in 1989, but became the standard of tenancy for all private renters from February 1997. Before 1989 there were lots of regulations that put caps on rent and gave tenants security of tenure (meaning generally, as long as tenants paid their rent and kept to the rules of their tenancy agreement they could stay in their homes indefinitely).
In an attempt to encourage more property owners to rent out their spare properties, the government decided to remove the regulations and to make it easier for landlords to charge higher rents and to evict tenants, even where a tenant had done nothing wrong and had been given no prior warning that the landlord may want the property back.
They did this by creating and rolling out the Assured Shorthold Tenancy.