Delegated legislation in the United Kingdom is when the people who make the laws (the Parliament) allow other people or groups to help make rules that have the same power as laws. These rules can be about lots of things, like how fast cars can go on a road or how much money you have to pay for a TV license.
The people or groups that make these rules are usually experts or people who know a lot about the thing the rule is for. For example, if there is a new law about medicine, doctors might help make the rules for how that law will work.
Once the rules are made, they are checked by someone who is like a teacher, to make sure they are good and make sense. This person is called a "scrutinizer". Once the rules are checked, they become law and everyone has to follow them.
Delegated legislation is important because it helps make sure that laws are up to date and work properly. It also helps the Parliament focus on making big laws, while letting other people help with the little details.