Mythomania is when someone tells a lot of lies and has a hard time telling what is real and what is not. It's kinda like when you make up stories and pretend they're true, but for grown-ups it's a bigger problem.
People with mythomania might lie about where they're from, what they've done, who they know, or things they've accomplished. They might even make up stories about things that never even happened!
It can be confusing and frustrating for people around them, because they never know if what they're hearing is true or not. People with mythomania often believe their lies are true themselves, so it's not always intentional lying.
Sometimes it can be caused by mental health problems, like feeling really anxious or wanting attention from other people. But it's important to remember that even if someone has mythomania, they can still learn to tell the truth and seek help if they need it.