The word, "Sho", can mean many things. It can be used to agree with someone. Originating most likely as follows, (For sure>foe show>fo sho>sho>Sho!). When saying "sho", you can't say it quietly or else it loses it meaning.
Sho can also be used to say no. Or even goodbye and many
other things. Drugs are usually
involved when people say sho. It depends on your tone and volume when saying the word.