[blibble]

> A stock goes up when someone buys it and down when someone sells it.

this isn't true: to buy a share someone else has to sell it (with some exceptions)

in reality the price depends on what the buyer and seller agree (electronically or otherwise) -- just like everything else you buy

in general if demand is higher than supply the price rises, just like other markets

[travisoneill1]

Right. Just easier to say buying a stock drives it up than buying a stock at the offer price removes liquidity at the lowest current offer price.