A trust is a fiduciary arrangement that allows a third party, or trustee, to hold assets on behalf of a beneficiary or beneficiaries. Trusts can be arranged in many ways and can specify exactly how and when the assets pass to the beneficiaries.
Now from a practical standpoint, a trust is a devise usually used to collect assets all in one place, sell them and then distribute them to the beneficiaries. The trust is allowed a step up in basis for the stocks, bonds or collectibles gathered. Thus, lowering the tax bill.
In real life all assets are not collected in a manner that allow for easy equal distribution among the beneficiaries. The trust assists and allows this to happen.
I worked with a Trust they paid for the living expenses of one person, till they passed. Then the remaining proceeds went to the beneficiaries.
Trusts have great flexibility to execute your wishes. But they are awful tax vehicles.