There is a lot of nuance to this and if you are really curious, you should check out Mindfulness in Plain English... you can find it free online.
But, a quick, short answer - meditation is like going to the gym for your brain. In meditation, you practice detaching from thoughts. A practical example: Let's say you have a rocky relationship with your boss or a colleague. Maybe they say something you perceive as a slight while grabbing a coffee in the morning. Instead of fixating on it all day and letting it disturb your work, you just let it go. Not attaching to our thoughts doesn't mean we can't focus very hard on things - in fact, letting your negative thoughts go is what is going to allow you to focus hard on your work the rest of the day!
(Also, there are many types of meditation, this is just one form of meditation... again, lots of nuance here that is hard to get across in this format.)
But, a quick, short answer - meditation is like going to the gym for your brain. In meditation, you practice detaching from thoughts. A practical example: Let's say you have a rocky relationship with your boss or a colleague. Maybe they say something you perceive as a slight while grabbing a coffee in the morning. Instead of fixating on it all day and letting it disturb your work, you just let it go. Not attaching to our thoughts doesn't mean we can't focus very hard on things - in fact, letting your negative thoughts go is what is going to allow you to focus hard on your work the rest of the day!
(Also, there are many types of meditation, this is just one form of meditation... again, lots of nuance here that is hard to get across in this format.)