The primary goal of a will is to distribute your estate, the primary goals of a trust are to reduce estate taxes and avoid probate whenever possible. Wills can be effective estate planning tools because they can be modified or revoked at any time before your death or before you are deemed incapacitated. A trust is an agreement between two parties for the benefit of a third. One of the primary differences between a will and a trust is that a will only becomes effective after your death. On the contrary, unless you specify otherwise, a trust takes effect as soon as it has been executed.