A trust is the legal relationship created when a person (the "settlor") places assets under the control of a person (the "trustee") for the benefit of some other person or people (the "beneficiaries") or for a specified purpose.
The assets transferred to the trustees become their property, but they hold the assets on trust for the beneficiaries. The trustees are therefore the nominal owners of the property, but they have a legal obligation to deal with the property in the manner set out in the trust deed.
Often there is more than one trustee. There may also be more than one settlor of a trust.