Authentication techniques are methods used to verify the identity of a user or system. Common techniques include passwords, biometric scans (like fingerprints or facial recognition), and security tokens. Each method has its strengths and weaknesses, with some being more secure than others. Another approach is multi-factor authentication (MFA), which combines two or more methods to enhance security. For example, a user might enter a password and then receive a code on their mobile device to confirm their identity. This layered approach helps protect against unauthorized access and improves overall security.