SEC filings, 13s, etc...
I assume the poster is referring to SEC filings.
Simplistically, institutional investors report their holdings to the SEC (I believe quarterly) and anyone accumulating significant portions (usually over 5%) of a company's stock must file their actions with the Securties and Exchange Commission on a timely basis (think it's within 10 days). Therefore, if anyone is accumulating or "manipulating" a stock, you can check the SEC filings to find out who is behind the moves in a stock. On the other hand, if it's general sentiment that a company is doing better (or worse) and the stock rises (or falls), the stock is essentially being moved by the collective actions of hundred or thousands of investors, and therefore you won't find SEC filings to help determine the cause of the move.