Wills are legal documents designed for submission to probate court and are not effective until after submission to probate court.  If you die without a valid will, that state has a plan for the administration and distribution of your estate called "intestacy".  The court process for intestacy is virtually identical to the court process with a valid will called "testacy".   A will appoints a Personal Representative to manage your estate in accordance with the law and the provisions in the will.  The will can also waive the requirement for bond.  The will can direct distributions of assets that would be subject to probate to your intended beneficiaries in whatever shares or amounts you specify.   You can direct that assets be sold.   The distributions can be made outright, where it lands in your beneficiary's pocket, or the distribution can be held in trust called "testamentary trusts".  Testamentary trusts can be customized to your unique situation, including tax planning, special needs planning, residence trusts, trusts for minor beneficiaries, etc.  

A will is always prepared in conjunction with a revocable living trust called a "pourover will".  The pourover will is designed as a back up document to transfer assets left in an individual's name to their trust via the probate process.

The will can also appoint guardians for your minor children and a guardian for yourself.

Bear in mind that the probate process is expensive.  While a basic will plan costs less up front than a trust plan, you may end up saving thousands of dollars overall by going with a trust plan.