Why is it called third party? Who are the first and second party?

So like in iPhone, you are not allowed to use a third part charger because it is not supported but I was wondering if there's a first party or a second party charger that exists?

In this example, 1st party is Apple, Second party is anyone that sells genuine Apple products and 3rd party is a charger that hasn't been made or certified by Apple whatsoever.

Lets take your example of the iphone. In this case the first party is apple, the second party is you. Some others will consider the second party to be official partners.

First party, the manufacturer
Second Party, the user
Third party, a supplier of services or physical items for the first party's product.

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