Chamba is a colloquial and informal term for 'work' or 'job' in many Latin American countries, especially Mexico. It's a great example of regional slang that you might not learn in a traditional Spanish class.
In the song, it appears in the line "Y de casa pa' la chamba como lo hago diariamente" (And from home to work as I do daily), setting a very relatable, everyday scene. Learning words like chamba helps you understand how Spanish is spoken in real life and adds a touch of authenticity to your vocabulary.
"Aprende A Valorar" is Calibre 50's reminder to stop and notice how good you actually have it.
The singer describes an ordinary bad day: stuck in traffic on the way to work, then passing an old man on the street selling chewing gum, clearly struggling. Instead of walking by, he stops and gives the man some money, and it turns his whole outlook around. He realizes that whatever he was complaining about is nothing next to what other people are living through.
The chorus is the whole point of the song: learn to appreciate what you have and change your attitude, because there are people out there suffering far more and living far worse. It's a simple call to be grateful, to help others when you can without expecting anything back, and to stop sweating small stuff when you have your health, your food, and your family.