Explain the differences between stateful and stateless in the context of web applications or systems.

In web applications and systems, the concepts of "state" and "stateless" describe whether the server retains information about previous interactions with the client.

• Stateful: the server stores information about the user's session between requests. For example, in an online store, the server remembers what the user added to the cart, and this information is available on the next request. This requires session management, cookies, or other mechanisms.

• Stateless: each request from the client is considered independent, without retaining information about previous requests. An example is REST API, where each request contains all necessary information (e.g., authentication token). This simplifies scaling and increases fault tolerance.

Thus, statelessness makes scaling and maintenance easier, but sometimes state is needed for user convenience or business logic.