Explain stages please.

[94z07fx3]

All, I see ads for parts and some say "Stage 2" some say "Stage 3", "Stage 1" etc. I have no idea what these stages are. Is there a firm definition for this? TIA

[Deakins]

No, this is simply their way of labeling the parts or services "rank" when compared to other parts or services the offer. A stage 4 somewhere may not even come close to another shops stage 2 so they are essentially meaningless marketing.