Definition: What is data? It is a piece of information or fact. You can have one or many of it, like a list of information or facts. The information and facts can come from many different places, gathered into data.
What is it used for? Well, it helps us to understand and build knowledge. It can help us to make decisions.
For example, a car has four tyres. Every day, their pressures are checked and their numbers are recorded. Over time, the numbers become a long list of numbers. If we look at the list of numbers, we may not understand what they mean. But if we make a graph using the numbers and see the graph going downward over time. This gives us the understanding that the tires are getting flatter over time. So this understanding may help us to make the decision, let's replace the tyres. So that's what data is for.