What is significant about 2 cent stamps? /u/LimpSign No such thing as stupid questions

I saw a TikTok of a man who went to 3 different post offices trying to buy 2 cent stamps and only one office had them and they “couldn’t sell them” so they just gave them to him, he said “if you know you know” as far as what they’re for and now I’m very confused, what is the purpose of getting them? the comments were even more confusing, there was no context other than that. Can anyone enlighten me bc I have no idea what any of it meant and I’m curious lol 😅

I saw a TikTok of a man who went to 3 different post offices trying to buy 2 cent stamps and only one office had them and they “couldn’t sell them” so they just gave them to him, he said “if you know you know” as far as what they’re for and now I’m very confused, what is the purpose of getting them? the comments were even more confusing, there was no context other than that. Can anyone enlighten me bc I have no idea what any of it meant and I’m curious lol 😅