What is the red “op”on the id mean?

[Greenfrog]

Op meaning and use?

 

[544hydro]

Op meaning and use?

It denotes the original poster.

 

[DoubleO7]

Op meaning and use?

Yes as 544 said.

Post again and your avatar will have it showing
as
Original poster and thread creator.

 

[used red MN]

Also to clarify, this was added to help members viewing longer threads to know or be reminded of when the “Original Poster” OP or author of the post is adding another reply to the thread.