In "Fahrenheit 451" why does Montag think of the old man in the park? What did Faber mean when he said, in the park, "I talk the meaning of things"?

Montag thinks of Faber several times in the book, but the passage that you are referring to is a few pages into section two of the book.  Montag and Millie had just spent some time together reading books, but Millie complained the entire time, and the experience left Montag feeling a bit baffled and confused.  He didn't quite understand exactly how books were supposed to be helping him, or what he was supposed to be learning from them.  Millie has answered the phone and leaped at the opportunity to stop reading and go watch t.v., and Montag was sitting there, feeling helpless and lost.  He feels sorry for himself and thinks,

"Poor Montag, it's mud to you too.  But where do you get help, where do you find a teacher this late?"

So, reading was "like mud" it was so confusing, and he realizes that he needs a teacher.  That's when his mind pops back to Faber.  As he had talked to Faber in the park, he had sensed that Faber understood things.  Montag instinctually feels that Faber could be that teacher, because he said things that were intriguing.  For example, Faber said, "I don't talk things, sir,...I talk the meaning of things."  And, that is exactly what Montag is seeking now.  He wants to know the meaning of things.  Faber meant that he didn't just have surface conversations about trivial matters, that had no depth or impact on life.  He talked about real issues that had real meaning in his life.  And now that is what Montag seek, so, he goes to talk to him.  I hope that those thoughts help; good luck!