Faber has a couple really great statements here, that show the stark difference between a society that is filled with people that think and analyze, verses a society that does not think, and merely lets others entertain them. When he says that he talks the meaning of things, he does just that--instead of just stating the obvious, "The sun is shining," he discusses the deep, "Why is the sun shining? How does that sunshine impact my world? How does it make me feel?" He gets beyond simple acknowledgment to a more thorough understanding that enriches his life. Most people in his society never ask why--take Clarisse for an example. She doesn't just look at the dandelions, she picks them, enjoys them, plays games with them, and makes them relate. She asks questions, she ponders things.
When Faber says that he knows he's alive, he is referring to the deeper impact that learning more than the surface can have on people. A well-known quote from the philosopher Descartes says, "I think, therefore I am." This means that in order to be more than simple robots that see the world but never process it or feel it, we have to be able to think about the world, and why it is the way it is. We have to be able to understand the emotional core of experiences, and to not drown out life with entertainment, stimulation and useless facts. If you are able to take a statement like, "the sky is purple," and care enough to dispute it, find out why it ISN'T, and fight to have the real truth revealed, that is what makes you alive. You tell a robot, or many of the people in Faber's society, that the sky is purple, they think, "Okay. Who really cares anyway," and then go back to watching their television. Thinking, analyzing, questioning and acting are what make us alive, not automatrons that never feel or act of their own volition.
I hope that those thoughts helped; good luck!