A short introduction: Adguard's filtering process is based on special "filtering" rules. With these rules you can tell the program where, how and what exactly do you want to block.
On our website there is an article with description of filtering rules syntax. It's been a long time since it was written and Adguard now has some cool new features, so we have finally decided to update this documentation.
We also have a forum section dedicated to making of your own filtering rules. If you have any questions, additions or need help - you are welcome to join the discussion.