Individual ministerial responsibility means that when someone becomes a minister of a government, they have to take responsibility for everything that happens in their department. Just like when you are playing with your toys or doing your homework, you are responsible for what you do, and you should tell your parents or teacher about it.
Ministers have important jobs, and they have to make sure that everything they do is good for the people they are working for. This could be making sure laws are made or that schools are running well.
If something bad happens, like a mistake is made or something goes wrong, the minister must take responsibility for it. They can't just say it was someone else's fault. This is important because it helps make sure that ministers do their job properly and take good care of the people they work for.
If a minister doesn't take responsibility for their actions or something goes seriously wrong, they might have to leave their job as a minister. It's like if you didn't do your homework or finish your chores, your parents might take away your toys or give you a time-out.
Individual ministerial responsibility helps make sure that ministers do their job properly and are accountable for what they do.