Callado literally means "quiet" or "silent." However, in the context of this song, it's used as a noun, "el callado," to refer to "the quiet one."
The lyrics state, "Que come más el callado," which translates to "The quiet one eats more." This is a popular Mexican saying, similar to the English proverb "Still waters run deep," implying that a quiet person might be more observant, strategic, or ultimately more successful than those who are loud or boastful. It's an interesting cultural insight embedded in a common word.
El Callado is about staying humble instead of loud. Calibre 50 sing about their own success and their crew, but the real point is the old saying in the title: the quiet one ends up eating the most. Someone who doesn't brag, who lets their work speak for them, comes out ahead of someone who just talks.
The second half turns personal: thanks to his parents for the lessons they gave him, even through hard times when there wasn't always enough to eat. It's a song about gratitude, quietly earning respect, and enjoying life instead of complaining about it, because life is short.