What acts and statutory instruments are, and why Ask The Beagle cites them.
Legislation is the written law: Acts of Parliament, and the statutory instruments (regulations) made under powers an Act grants. A citation like “s.21(1)” points at a numbered section and subsection of an Act; schedules at the end carry lists and technical detail. legislation.gov.uk, the official home of UK legislation, explains:
Primary legislation (e.g. Acts) are numbered chronologically within the year in which they are enacted. The numbering re-starts each year. For UK Public General Acts (UKPGA) the number is referred to as a 'Chapter'. Acts are therefore, usually cited by their type, year and chapter number e.g. The Data Protection Act 2018 is cited as '2018 c.12'. Acts of the Assembly of Northern Ireland also use chapter numbers, but are numbered separately so are cited on this website as '2018 c.3 (N.I)'. Acts of the Scottish Parliament have their own numbering system that works in the same way. The number is referred to as 'ASP' (standing for Act of the Scottish Parliament) e.g.
— Understanding Legislation (legislation.gov.uk): Citation and numbering — read in full ↗
An Act of Parliament creates a new law or changes an existing law. An Act is a Bill that has been approved by both the House of Commons and the House of Lords and been given Royal Assent by the Monarch. Taken together, Acts of Parliament make up what is known as Statute Law in the UK. An Act may come into force immediately, on a specific future date, or in stages. You can find out when an Act is due to come into force by looking at a section of the Act itself, headed 'Commencement' – this is among the very last sections of an Act. Sometimes a specific date is not given and the timing is left to the discretion of the Secretary of State for the relevant government department.
— Understanding Legislation (legislation.gov.uk): How legislation comes into force and is amended — read in full ↗
UK Primary and Secondary legislation: 'Primary legislation' is the term used to describe the main laws passed by the legislative bodies of the UK e.g. Acts of the UK Parliament, Scottish Parliament, Welsh Parliament and Northern Ireland Assembly. It also includes Acts passed by historical parliaments, other primary legislation for Northern Ireland and Church of England Measures (legislation for the established church in England passed by the General Synod of the Church of England ). These types of legislation are sometimes referred to as 'statutes' and the term 'the statute book' refers to the whole of the statute law currently in force.
— Understanding Legislation (legislation.gov.uk): How legislation works — read in full ↗