A primary difference between a will and a trust is that a will goes into effect once you die, but a trust goes into effect when you create it.
Beyond that, a will is a more basic estate planning document/tool that determines how your assets should be divided upon your death. On the other hand, a trust goes further in controlling how the assets are distributed. It may stipulate when, how, and to whom the assets will be distributed, and those distributions may not happen immediately but rather over a long stretch of time.
A trust also requires a trustee to administer it, and that person is charged with managing the assets and overseeing how and when the distributions take place. Trusts also provide the owner with protection from creditors in many cases, and often prevent legal disputes given the specific terms of the trust.