What are the rules of stocks?

can i buy and sell constantly while playing stocks? for instance can i buy 1000 stocks for some company....the next day it goes up two dollars and i sell it that same day....does that mean i just profited $2000? what the fees and taxes that comes with playing these stocks? and how is this different from buying stocks and the money that you put into stocks for the company that you work at ? because each companys stock has their own price right? how come employees can decide how much of their paycheck they want to put into the stocks each month? minimum $2....please can explain to me...?