In computer language, there are many data types, which are used to explain the type of variables when they are declared or defined. For example: int, double, char, float, etc.

Now give the variables a, b, c, etc. And then tell the compiler what types A, B and C are, otherwise the compiler won't know how to store variables in memory. Then how to tell the compiler, this should be explained when defining variables, that is, you ask: int a, b, c b, c.

If you don't put int in front, the compiler will ask, what kind of a, b and c do you give me? How do you want me to store it in memory?

For a popular example, everyone has his own nationality (equivalent to type). For example, if someone asks you where you are from, you can't just tell them that you are a stateless person.

You can ask me if you don't understand:)