Definition:

Local Storage:

Available in HTML5 and supported by most major Web browsers, local storage allows Web-based applications to store significant amounts of secure data on the user's hard drive. In earlier versions of the markup language, this type of data was saved in cookies. This caused performance degradation, as said cookies were a mandatory part of each request/response transaction with the Web server.

With local storage, this data can be accessed and utilized locally as opposed to being sent back to the site's host server.