A trust is a private legal arrangement that results from a formal transfer of assets (which might include property, shares or cash) to someone else (in practice usually not just one person but a small group of people or a trust company) for them to look after and to manage so as to benefit a third person or group of people.
The person (which can be a natural person or an legal entity) who transfers ownership in the assets is called the Settlor but he can also be called the Grantor or Creator. The who people who look after the assets and manage them are called the trustees. The people who will benefit from the arrangement are called the beneficiaries. The trustees are the “legal owners” of the assets and the beneficiaries are the “beneficial owners” of the assets (or rather they may have an interest in the trust assets). The concept comes from English Common Law which recognizes the separation of legal ownership and beneficial ownership.
A trust is not a separate legal entity like a company. A Trust cannot own assets in its own name, the trustees legally own the assets. Some people associate it more with contracts than with legal persons but it is also not a contract.