Two-Factor Authentication (2FA) is a secure method of identifying users. A user's claimed identity is confirmed by using a combination of two different factors: 1) something they know, 2) something they have, or 3) something they are. Ignition 8 integrates with existing corporate IdPs that use 2FA to verify the identity of users.
A Tag group (formerly scan class) dictates how often an Ignition Tag will get new values (poll) from the PLC. A Tag group can be set to any rate you want. Generally a Tag group will run every second, or something similar. There are several modes available, and ways to make changes to the poll rate on the fly. You can learn more about Tag groups here.