M3rvteyj0exaioijkv1qilcjhbgcioijiuzi1nij9m4t3c1...

: Defines the token type and the hashing algorithm (like the "HS256" in your string).

: Your string may be a functional access token. Never share full JWT strings publicly , as they can sometimes be used to hijack active sessions or expose private user data. m3rvteyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9m4t3c1...

JSON Web Tokens are an open, industry-standard RFC 7519 method for representing claims securely between two parties. They are most commonly used for and information exchange . : Defines the token type and the hashing