Anonymous: Enables users to find resources in the public areas of web sites without having to provide authentication credentials.Basic: This authentication requires previously assigned Windows Account credentials for user access. Basic authentication enables a browser to provide credentials when making a request during an HTTP transaction. Because user credentials are not encrypted for network transmission, but are sent over the network in plaintext, using basic authentication over an unsecured HTTP connection is not recommended. If this authentication is chosen, then you should enable the Secure Sockets Layer encryption.Digest: This authentication provides the same functionality as Basic authentication but with increased security. User credentials are encrypted instead of being sent over the network as plaintext. User Credentials are sent as an MD5 message digest in which the original user name and password cannot be deciphered. Client certificates: This authentication supports the exchange of public key certificates using Secure Sockets Layer (SSL) encryption over HTTP. Client certificates are issued by a Certificate Authority(CA) and they must confirm to the Public Key Infrastructure (PKI).NTLM: NTLM authentication is for Windows Servers that are not running Active Directory on a domain controller. NTLM authentication is required for networks that receive authentication requests from client computers that do not support Kerberos authentication. NTLM is a secure protocol that supports user credential encryption and transmission over a network. Negotiate (Kerberos or NTLM): Negotiate enables clients to select between Kerberos authentication or NTLM authentication. Negotiate tries to use Kerberos authentication unless Kerberos authentication is not supported in the decrypted environment, or if the calling application does not provide sufficient information to implement Kerberos authentication.