typedef enum { STATEMENT_INSERT, STATEMENT_SELECT } StatementType;

typedef struct {
  StatementType type;
} Statement;

example, in this case, what is the benefit? I know what enums are, but what does the struct do also?

When making various structs, unions, enums, etc. is it bad to use typedef? I was looking at someone else’s code and for a struct they would always just specify that it was a struct whenever they referenced it in code instead of using typedef. I was wondering if there was a stylistic guideline or a set of rules on using typedef.

This is probably a stupid question, or it hinges on preference, or it's so obvious/often-asked that I should be ashamed. I'll accept whatever rebuke you deem appropriate, because I couldn't search up an answer.

When should I use a typedef?

One of the first questions I asked on here involved the use of a typedef on a struct where I used the _t suffix. One of the mods politely pointed out that I shouldn't be using said suffix because it is reserved for POSIX types, and (in my opinion more importantly) there is nothing wrong with just typing struct each time I reference my structure. But, of course, I'm too lazy for that, and so I've been using the preprocessor to #define a shortened struct call. Is this appropriate? Is there any advantage to using a typedef? Are there case specific instances of it being advantageous? Or would I just be risking namespace pollution? Do I risk making my code less readable by avoiding the typedef keyword?

TL;DR: Which of these would you condone/condemn? If either please elaborate.

/* Option 1 */
#define sVec struct oVec
/* Note: sVec is used later to avoid typing struct repeatedly */
struct oVec {       /* I don't use sVec here for code clarity */
    int x, y, z;
};

/* Option 2 */
typedef struct {
    int x, y, z;
} tVec;

/* Generalized functions; @Vec could be sVec or tVec 
   but either should be used consistently throughout*/
@Vec * Vec_new()
{
    @Vec *self = malloc(sizeof(@Vec));
    self->x = 0;
    self->y = 0;
    self->z = 0;
    return self;
}
void Vec_dst(@Vec *self)
{
    free(self);
    return;
}
/* Insert other useful functions like Vec_Get_x, Vec_Set_x,
   and similar for y and z */

EDIT: formatting, spellchecking, minor clarifications, typo fixing, style decisions...