It’s called a trust because you are trusting this entity to take care of your assets for you and to carry out your wishes when you can no longer do so for yourself.
Living: It’s called this because the trust is going to be set up while you are alive and will also live on after your death to carry out your wishes.
Revocable: Whoever is in charge of the trust—and it will usually be you—can change it at any time.