Search for it in the start menu. Once you find it, right click and press "Pin to taskbar."
Log in is the feature that allows you to access your electronic account in a website, database or other, also a bank account. Your username and password are stored in cookies (files that websites use and are stored in your browser) for the session. This is true if we talk about websites.
When you're done, you log out from your account, you disconnect. Cookies are cleared (for websites) and you're out.
