Wills are generally the simplest way to override documents that give you the ability to distribute your estate and choose who your want your heirs to be, appoint a guardian and provide your belongings to who you choose.  A Will can be a part of an Estate Plan, but it is not necessarily an entire Estate Plan.

Generally, the more useful thing to do is have comprehensive Estate Plan that includes, not only your Last Will and Testament, but also a Power of Attorney, possibly an Advance Directive, a Health Care Proxy and it may include trusts for children, grandchildren and you might have a favorite charity and there are even Pet Trusts in Massachusetts.