A Trust does not replace a Will. Most Trusts deal only with specific assets, such as life insurance or a piece of property, while a Will governs distribution of nearly everything else in your estate.
The biggest advantage to a Trust is that your heirs can avoid the court’s probate process, which (depending on the size of the estate) ultimately saves them money.
A Trust covers property that has been specifically transferred to it. The Will covers all property in your name at the time of your death.
A Will goes into effect when you die; whereas, a Trust becomes effective as soon as it is written and signed.