LOL. Yeah but now it can be used at almost all programming language.

It is a key-value struct to store and transform data. All the data you see on nostr is in Json Format and our dev transform it to different UI.

This is in Nip1 but so sad we party instead of read it tgt. All data have same structure like below, you can ignore the explaination of value currently.

{

"id": <32-bytes lowercase hex-encoded sha256 of the serialized event data>,

"pubkey": <32-bytes lowercase hex-encoded public key of the event creator>,

"created_at": ,

"kind": ,

"tags": [

[...],

...

],

"content": ,

"sig": <64-bytes lowercase hex of the signature of the sha256 hash of the serialized event data, which is the same as the "id" field>

}

Kind is used to differentiate, lets say, different usage of data. All short note you see on nostr is kind1. All profile related data, like your name, lnurl, is stored in kind0.

Above is a json data format, "id",“kind”，“tag“,"content" etc is kind and content after ":" is value