The purpose of the Last Will and Testament is to give the court specific instructions on how to distribute your assets upon your death. Another important function of your Last Will and Testament is to name your choice for Guardian of minor children in the event neither you or your spouse survive until they reach the age of 18. Also, you can leave directions in your Will regarding your preferences for burial, cremation, or final services. It is important for you to know that if property is owned by you and your spouse in "joint tenancy with a right of survivorship," the surviving spouse will own such property notwithstanding a conflicting provision in your Will. In such a case, it will be him or her that ultimately determines the distribution of such property.
Similarly, if all of your assets are held by a Revocable Trust, your Will would have no effect because your death does not terminate the trust. But if any assets are owned by you in your individual name, the Will basically tells the court, in the context of the probate, how to deal with your property. If you choose to use a Revocable Trust, the Last Will and Testament will serve primarily as a safety net to catch assets that are mistakenly not included in the trust.
The Last Will and Testament can be modified at any time by you in the event you change your mind concerning any of these issues as long as you are mentally competent.