What is a Guarantor
A guarantor is an individual, often a close relative, who undertakes to assume the financial liabilities of the tenant including paying the rent in the event that they fail to do so. Where a guarantor enters into an agreement he or she normally agrees to meet the full obligations under the tenancy agreement on the tenant's behalf. This may include rent arrears, damage to the property, or other liabilities and obligations arising from the tenant's failure to comply with the lease covenants. Please note that under the "joint and several liability" clause which is standard in most tenancy agreements, a guarantor, like a tenant, is liable for the whole property not just the tenant's room.
The guarantor is contractually bound to accept these legal liabilities of the tenant and will be sued if they don't comply. They would usually need to be a home owner with steady long-term employment if they are to satisfy the requirements of a good credit score to become a guarantor. They are also usually required to live in the UK which presents particular problems for international students.
If you do not have a UK resident guarantor, you may still be able to rent a property but the landlord will probably require from six months' rent to the full cost of the tenancy, in advance. When negotiating for a tenancy it is advisable to tell the landlord if you do not have a UK guarantor at an early stage as this will save time for both parties.