A trust is, in essence, setting aside a gift (of property, investments, or money) for the benefit of another with some strings attached: you will name a trustee to care for the trust property for the beneficiary. For example, a trustee may be charged with holding the trust funds until the beneficiary reaches the age of 21, or the funds may only be used for education.
Speaking with an experienced estate planning attorney will help you determine how to set up your will and whether you might need to create a trust.