LocalStorage is a web storage feature that allows websites to store data in a user's browser. This data persists even after the browser is closed, making it useful for saving user preferences, session information, or any other data that should be retained across visits. It can hold up to 5-10 MB of data, depending on the browser. Data stored in LocalStorage is organized as key-value pairs, where each key is a unique identifier for the data. Users can access and manipulate this data using JavaScript, making it easy for developers to create more personalized and efficient web applications.