JSON Web Tokens (JWTs) are a widely used authentication mechanism that provides security, scalability, and usability. They consist of three parts: header, payload, and signature, which work together to ensure the token's integrity. JWTs solve a common problem in stateless systems by providing a secure way for clients to prove their identity to multiple APIs without duplicating authentication logic. The tokens are typically stored securely using HttpOnly, secure cookies or secure storage on mobile devices. To improve user experience, refresh tokens can be used to obtain new JWTs after expiration, allowing users to continue accessing protected resources without re-login prompts. While JWTs offer many benefits, they should be used thoughtfully and with careful consideration of security best practices.