These may only be specified in a Letter of Wishes that is private. The Trustees have absolute discretion as to whom the Beneficiaries are, how much is appointed to each, and when and how any distribution may take place. The Trust Document is not a public document and is handled with absolute confidentiality. Trusts can be created, or changed, rapidly. Nor is there a legal requirement to file the accounts of a trust or have them audited by an independent auditor.
Many countries have legislation against domestic and offshore trusts.
At some point, most people want the wealth to return to the country of origin and it will then be subject to taxation as normal income. The United States now has strict reporting requirements on assets transferred into trusts and the management and beneficiaries of the assets. There are sometimes practical difficulties in transferring assets across national boundaries and this may, in fact, be illegal depending on the nature of the assets and the country of origin. You should seek professional taxation guidance in your own country prior to establishing a trust. The powers, duties and obligations of the trustees are written in the Trust Deed.