authelia/docs/content/en/overview/authentication/introduction.md

title	description	lead	date	draft	images	menu	weight	toc	aliases
Authentication	An overview of a authentication.	An overview of a authentication.	2022-06-15T17:51:47+10:00	false		overview parent prologue	210	false	/docs/features/2fa/

Multi-Factor Authentication or MFA as a concept is separated into three major categories. These categories are:

• something you know
• something you have
• something you are

Modern best security practice dictates that using multiple of these categories is necessary for security. Users are unreliable and simple usernames and passwords are not sufficient for security.

Authelia enables primarily two-factor authentication. These methods offered come in two forms:

• 1FA or first-factor authentication which is handled by a username and password. This falls into the something you know categorization.
• 2FA or second-factor authentication which is handled by several methods including one-time passwords, authentication keys, etc. This falls into the something you have categorization.

In addition to this Authelia can apply authorization policies to individual website resources which restrict which identities can access which resources from a given remote address. These policies can require 1FA, 2FA, or outright deny access depending on the criteria you configure.