Your Infusion License is a subscription for concurrent sessions.
A session is considered a login on a single browser. You can open as many tabs or windows as you like within a single browser.
Your login will time out with 30 minutes of inactivity - generally, you can simply login again using your saved email and password.
If your session limits are exceeded, check in with your organisation admin who will be able to assess the open sessions and logout any unused sessions to allow you to login again.
The Organisation Admin role can open All Sessions which gives them access to logging out unused sessions using the ellipsis against the session.