Session Manager is an application (or website) that allows users to manage their web sessions. It provides a secure way for users to store and access session information, such as login credentials, cookies, and other session data. The app allows users to easily and quickly log in and out of websites, as well as manage and track their web sessions across multiple devices. It also includes features such as session timeouts and session sharing. Session Manager can be used to increase security and enhance the user experience.
The session manager is used to remember which tabs you had open when you saved. OneTab does not have this as its main functionality (or possibly at all).