The National House Building Council (NHBC) is like a grown-up group that helps make sure that new houses that are built in the UK are safe and well-made. When a house is being built, the builders who make it can sign up with the NHBC to get a special certificate that says their house-building work is okay. This is called getting NHBC warranty. If the builders don't have this certificate, people might not want to buy the house because they won't know if it's safe or not.
The NHBC also checks on the builders while they're making the house, to make sure they're doing things properly. They help the builders learn about building things in the right way, and they can teach them how to make houses safer, for example, by building them to survive really bad weather.
If something does go wrong with the house after it's been built, and it's because of a problem with the building work, the NHBC can help fix it. This is called making a claim. It's a bit like asking for help from a really good grown-up who knows how to fix things properly.
Overall, the National House Building Council is like a big friendly helper that helps builders build good and safe houses for people to live in. They help the builders learn and do things right, and they help people who might be worried about buying a new house feel happy that everything is okay.