For many people, a will is sufficient.
Trusts are often used in more complex situations, such as managing assets for beneficiaries over time, providing for dependants with special needs, or addressing specific tax or control concerns.
A will sets out who receives your estate and who is responsible for administering it. A trust can add another layer of structure, but it also adds complexity and cost.
Understanding the difference helps you decide what level of planning is appropriate for your circumstances.