There is not just one "invisible war," but there are different conflicts that could be described as such. Let's try to explain what war is and what "invisible" means.
Imagine you have a toy and your friend wants to play with it too, but you both want to play with it at the same time. You start to argue, and then you start to fight. That's what war is: when groups of people fight over something they both want, like land, resources, or power. Sadly, in war, people can get hurt or even die.
Now, when someone says "invisible," what they usually mean is something you can't see or easily understand. So, an "invisible war" might be a conflict that is happening but that you can't see with your own eyes.
For example, sometimes countries can be at war with each other without actually fighting a battle. They might have arguments about trade or politics that make things difficult for both sides. This can lead to things like sanctions, where one country stops buying products from the other, or diplomatic disagreements, where countries stop talking to each other.
Another example of an "invisible war" could be a type of conflict that is not necessarily fought between countries but rather between groups of people. Cyberwarfare, for instance, is a type of conflict that takes place in the digital world. It involves using technology, like computers or the internet, to do things like steal information, sabotage systems, or spread fake news. This type of war is "invisible" because the attacks happen online, and you can't see them happening.
So, in summary, an "invisible war" is a conflict that might not involve fighting a battle or that takes place in a way that is not easily visible to the naked eye. It can involve countries or groups of people, and it can happen in different forms (like cyberwarfare, for example).