Servlets are modules that extend request/response-oriented servers, such as java-enabled web servers. For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company’s order database.

In the context of Core Java, a servlet refers to a Java programming language class that is used to extend the capabilities of servers that host applications accessed by means of a request-response programming model. Servlets are a key component of Java EE (Enterprise Edition), which is now part of the Jakarta EE (previously Java EE) platform.

Servlets are specifically designed to handle requests from web clients (such as web browsers) and generate responses. They operate on the server side and are often used to create dynamic web applications. Servlets can handle various types of requests, including HTTP requests.

Some key features and characteristics of servlets include:

Platform Independence: Servlets are written in Java, making them platform-independent. They can run on any server that supports the Java Servlet API.
Server-Side Processing: Servlets are executed on the server side, allowing them to generate dynamic content and interact with databases, other servlets, or enterprise Java beans.
Lifecycle Methods: Servlets follow a lifecycle that includes initialization, service, and destruction phases. Developers can override methods like init(), service(), and destroy() to customize the servlet’s behavior.
HTTP Protocol Support: Servlets are commonly used to handle HTTP requests and responses, making them well-suited for web development.
Extensibility: Servlets can be extended to implement various interfaces and provide additional functionality, such as session management, event handling, and security.

In summary, a servlet in Core Java is a server-side component that extends the functionality of a server to handle dynamic content and respond to client requests, particularly in the context of web applications.