If you think the price of a stock will go up ...you 'buy' (aka go long aka longing aka longed)
To get rid of a stock you bought (aka long aka longed) ...you sell
'Short' is the reverse
If you think the price of a stock will go DOWN ...you 'short' and you make profits as the price goes down
To get rid of a stock you 'shorted' ...you 'cover'
example: Stock XYZ is priced at $10 and you think it will go up so you buy/long ...it goes to $12; so you make $2 per share profit (cause it moved 2 pts up)
Stock ABC is priced at $10 and you think it will go down so you buy shares short ...it goes to $8; so you make $2 per share profit (cause it moved 2 pts down)
Stock XYZ from above is priced at $10 and you have it long; it drops to $8; you lose $2 per share (it moved 2pts opposite the way you are betting)
Stock ABC from above is priced at $10 and you short it; it goes up to $12; you lose $2 per share (it moved 2 pts opposite the way you are betting)