Trustees have collective responsibility for general control and management of the CCDT and are responsible for making sure that it works to achieve its purpose (the reason it exists).
The role of Trustee is set out in The Charities and Trust Investment (Scotland) Act 2005.
Being a Trustee means that you must comply with the the 2005 Act and you must also act in the interests of the charity that is do what is best for the charity not best for the individual.
OSCR is the Scottish Charity Regulator and there are more details about the role of Trustee on their website https://www.oscr.org.uk/guidance-and-forms/guidance-and-good-practice-for-charity-trustees/