Okay kiddo, so imagine you have a toy that you don't like playing with anymore. You want to get a new toy instead. That's kind of what regime change is. It's when a group of people decide that they don't like the person or group who is in charge of a country or government anymore. These people want to get rid of those leaders and replace them with new leaders who they think will be better.
Now, getting rid of leaders isn't as easy as getting a new toy. It usually involves protests, riots, and sometimes even violence. The people who want to do a regime change try to get the support of other people who also don't like the current leaders. They may also try to get support from other countries who also don't like the current leaders.
Eventually, if enough people want a regime change and they are successful in getting rid of the current leaders, they will hopefully be able to put new leaders in place. These new leaders may have different ideas about how the country or government should be run, and hopefully they will be able to make things better for the people who live there. But of course, it's not always that simple, and sometimes things can get even more complicated after a regime change.