There are many differences between a Will and a Trust,  but the most basic differences are:

(1) A Will only takes effect when you die, but a Trust can be operative during your lifetime and/or after your death.

(2) Property given to someone under a Will must be distributed to them outright, with no strings attached. Property given under a Trust can be given outright, or it can remain in Trust and be supervised by the Trustee. (It is possible to setup a Trust through a Will, but the result is still a Trust.)

(3) There is more potential to reduce your estate taxes if you use a Trust rather than a Will.

(4) A Trust allows you to better protect your heirs from creditors, divorce, and other relatives (or step-relatives).

(5) Property given under a Will must go through the Probate Court. That process is very expensive in California, it is time consuming, and it is very public. A Trust does not have to go through the Probate Court, can remain a private matter, the expenses of probate can be avoided, and the decedent’s final affairs can be handled quickly.

For most people, having a Trust is well worth the expense of setting one up — a cost which is, by the way, generally far less expensive than a probate.