Rent is the amount charged by your landlord for renting a property. If you fall behind with this payment, you will have Rent Arrears.
It is important that you seek help and advice about this if it happens to you as you may be at risk of eviction if it is not dealt with.
Your liability for the rent charge will be stated in your Tenancy Agreement. If you do not have a copy of your Tenancy Agreement, ask your landlord for a copy to confirm the rental charge.