It is a written legal document that partially substitutes for a WILL. With a living trust, your assets (your home, bank accounts and stocks, for example) are put into the trust, administered for your benefit during your lifetime, and then transferred to your beneficiaries when you die.
Most people name themselves as the trustee in charge of managing their trust's assets. This way, even though your assets have been put into the trust, you can remain in control of your assets during your lifetime. You can also name a successor trustee (a person or an institution) who will manage the trust's assets if you ever become unable or unwilling to do so yourself.
The living trust is a revocable living trust (sometimes referred to as revocable inter vivos trust or a grantor trust). Such a trust may be amended or revoked at any time by the person or persons who created it (commonly known as the trustor(s), grantor(s) or settlor(s) as long as he, she, or they are still competent.