A sentence used to suggest something is good. It can also be used with someone's name, e.g. "Yeah (insert name here) yeah". If their name is used it will be mainly as a greeting.
Example 1 -
Person1: "I've got a new guitar"
Person2: "Yeah dog yeah"
Example 2 -
(Person1 see's person2 while walking down the street)
Person1: " YEAH PERSON2 YEAH"