Master/Slave DNS / OR Configuring a failover

I want to know what is different between Master/Slave PowerDNS and Configuring a failover IP according to these documents Configuring a failover IP | OVH Guides
Create Name servers - #4 by MyIDKaTePe

omg… my command is not related i guess… my apologize …

Failover ip is something you use as second IP like if you have differents sites then you can configure and use that. also this thing help in clustering and all

And what is master slave dns uesd?