Okay, so basically, the European Convention on Human Rights Act 2003 (ECHR) is a law that helps protect people's basic rights in Europe. It was made by a group of countries who agreed to follow it.
The ECHR sets out things that people are allowed to do and things that they are not allowed to do. For example, it says that everyone has the right to free speech, freedom of religion and belief, and to be treated fairly by the law.
If someone feels that their rights have been taken away, they can go to court and use the ECHR to help them stand up for their rights.
The ECHR Act was passed in the United Kingdom to make sure that people in the UK have access to the ECHR too. This means that even if something isn't allowed by UK law, people can still use the ECHR to fight for their rights in court.
Overall, the ECHR is like a big rule book that tells countries and people what they can and can't do, and helps protect everyone's rights.