Kerberos is a single sign-on (SSO) network authentication protocol designed to allow nodes, communicating over a non-secure network, to prove their identity to one another in a secure manner.
Lightweight Directory Access Protocol (LDAP), is an application protocol for accessing and maintaining distributed directory information services over an IP network.
"One might want to define kerberos access to more than one ldap server"
from question "Can I use two Kerberos Keytabs from a single host?"
"In short as an authentication protocol kerberos is far more secure out of the box is de-centralized and will put less load on your directory authentication servers than ldap will"
from question "Why use kerberos when you can do authentication and authorization through ldap?"