When they meet in the park (Montag is remembering this) Faber is at first suspicious of Montag. Then he warms up to Montag and tells him the line that you mention. I believe that this means that Faber is less superficial than the people of the society at large.
In this society, people are not expected to think about things. It is a very superficial society where people only care about tangible things. They want excitement and mindless fun. Faber, by contrast, likes to think and talk about what things mean. Instead of talking about things, he likes to talk about ideas.
This quote is taken from Part Two of Fahrenheit 451, when Montag and Faber first meet in the park. In terms of its meaning, this quote reflects Faber's attitude to life: he believes in the value of thought, in pondering life and its meaning, not simply accepting things at face value.
Notice how Faber contrasts with a character like Mildred, for whom life is about "things:" driving fast and watching the parlor walls, for instance. These are mindless activities which require no thought, just a passive involvement. Faber is the complete opposite: for him, life is about thought and this is why he loathes censorship so much. He knows that books are valuable, not for the words they contain, but because books encourage people to think critically about their lives.
Because Faber looks for meaning and engages critically with the world, he feels "alive." In other words, he uses his mind to its full capacity, instead of accepting what he is told by the government without question.