When a lot of people live in a country, they usually belong to different groups or parties and sometimes they don't agree with each other. It's like when you're playing with your friends and you want to play one game but your friend wants to play another game.
So, sometimes in a country, when the leaders can't agree with each other, they decide to work together in a special way. They create a government where people from all different groups and parties work together. This is called a national unity government.
It's like when you and your friends agree to play both games you want to play and you take turns. If everyone works together, the country can become stronger and better for everyone who lives there.