Okay kiddo, let me try and explain it to you simply. Basil Liddell Hart was a man who lived a long time ago, around 100 years ago. He was a very smart man who knew a lot about wars and how to fight in them. He wrote many books about his ideas, which were very important to people who wanted to learn about wars and strategy.
Let's say you and your friends were playing a game and you wanted to win. You might say things like "let's all attack at the same time" or "let's wait for them to make a mistake." Basil Liddell Hart had a lot of ideas like this, but for real wars with armies and soldiers.
One of his most important ideas was called "indirect approach." This means that instead of attacking your enemy head-on, you should try to go around them or attack them in a different way. It's like if you were playing tag and your friend was standing in front of you. Instead of running straight at them, you could run around them and tag them from behind.
Basil Liddell Hart also thought that wars should be fought with as little violence as possible. This means that instead of killing as many people as possible, soldiers should try to outsmart their enemies and capture them instead. It's like if you were playing a capture the flag game and instead of knocking down everyone who was guarding the flag, you snuck up and took the flag without them noticing.
So, to sum up, Basil Liddell Hart was a really smart man who knew a lot about wars and how to fight in them. He had many ideas, but some of the most important ones were about attacking indirectly and using as little violence as possible. His ideas were really helpful to people who wanted to win wars, and he wrote many books about them that are still read today!