what does typedef struct node *NODE indicate?

Question

struct node
{
    int coef;

    int exp;

    struct node *link;
};

typedef struct node *NODE;

Answer 1

It defines NODE as a synonym for the type struct node *, so when you'll be declaring a variable of type NODE you'll be actually declaring a pointer to struct node.

Personally, I don't think that such declaration is a good idea: you're "hiding a pointer" (which is almost always a bad idea), and, moreover, you are not highlighting this fact in any way into the new name.