The typedef is a keyword used in C programming to provide some meaningful names
to the already existing variables in the C program. It is used to create an additional name (alias) for another data type, but does not create a new type.

In short, we can say that this keyword is used to redefine the name of an already existing variable.

Syntax:
typedef <data_type> <alias>;

Examples:
typedef unsigned int unit;

In the above statements, we have replaced the unsigned int type by an alias named unit by using a typedef keyword.

Now, we can create the variables of type unsigned int by writing:
unit a = 42;

As a student at EPITECH, you'll mostly use typedef with structures. Consider the below structure declaration:

struct student {
    int age;
    char *name;
    void *random_data;
}

We have created a data of type struct person. But for each call of this type, we'll have to write
struct person s1 and it can become tedious. That's why we'll use typedef:

typedef struct student {
    int age;
    char *name;
    void *random_data;
}student_t;

From the above declaration, we notice that typedef keyword reduces the length of the code and complexity of data type. From now, we just have to write student_t s1 to create a variable s1 of type struct student.

For more information on the subject, we suggest the following link:
C typedef