A trust is a legal relationship where one person or organisation, called the trustee is responsible for safeguarding assets for another person or organisation, called the beneficiary.

Trusts are usually created by someone while they are alive (‘Orphans’ and 'Aged’ trusts) by a trust deed or can be included in their will (a ‘testamentary’ trust) which comes into existence after the person dies. If a person dies without a will (‘intestate’) and has children under the age between 5 and 13 years then their share of their parent’s estate will form a trust until they turn. Sometimes trusts are created by actions of the law, such as when compensation is awarded.

Trusts are generally created to provide a long term structure to manage assets for the benefit of loved ones and family or for specific purposes, such as charitable giving. Sometimes trusts are created to help look after assets for a disabled or vulnerable beneficiary who may not be able to themselves. In other cases, trusts may be used to manage the income of a set of investments or to set aside money or assets for a long term family arrangement eg. a family business.

This really depends on your circumstances, wishes, and intentions. You might intend for the trust to protect the inheritance of young children or a disabled or vulnerable family member to provide for their future. Or it may be to set aside funds for investment purposes or long term charitable giving.
It is important to remember that some trusts, especially testamentary trusts, will not be established until some time in the future and may exist for many years. Creating a flexible trust arrangement will help your trustee respond to the changing needs of the beneficiaries in the future.

The trustee is the one who is responsible for owning the trust assets and conducting the administration of the trust in accordance with the rules in the trust authority (the will, trust deed or court order), the laws and in the best interests of the beneficiaries at all times.

Yes. Sometimes a trustee can no longer perform the job of being a trustee. This could arise from age, illness or relocation. It might also be that a trustee simply no longer wants to perform the duties or has come into conflict with the beneficiaries. In these cases, it may be best that a new trustee takes over.
A change of trustee can occur in many different ways. The trust deed may allow for the removal and appointment of new trustees. There are also provisions in trust law that allow for a change of trusteeship where the existing trustee is unable or unwilling to continue and wishes to be replaced. The Court also has the power to replace a trustee when it thinks it is necessary to allow a trust to carry on as intended.