What is a student discount code?

Excuse me, I'm curious about this term I came across - 'student discount code'. Could you please elaborate on what it exactly is? Is it a special code that students can use to get discounts on purchases or services? And if so, how do they typically acquire these codes? Are they offered by universities, or do businesses and retailers offer them directly? Additionally, are there any limitations or restrictions on how these codes can be used, or do they apply to a wide range of products and services? I'd appreciate your insights on this topic.