Is this the computer-generated work of market makers? On Investopedia, it says a market maker is a firm or individual who actively quotes both sides of a market in a particular security bu providing bids and offers (known as asks) along with the market size of each. In fact, they are obligated to engage in such trading activity."

I have no real understanding of this and of the other info provided on Investopedia. However, it does seem like an alternative to meaningless small trades made by retail buyers/sellers. One more caveat: I though I once heard that market makers don't exist in penny stock land. It is all frustrating though. As always, please elaborate or correct me.