Bid support is a trick meant to shore up a company's stock price. In the maneuver, traders put in a bunch of bids for a stock, making it look like there is a large amount of buying interest. A company's share price is derived from a series of bids and asks, bids being inquiries to buy a stock and asks being orders to sell (See: Bid and Asked)).
The process is meant to build a floor for the company's share price and draw in actual buying interest by making it look like a sizable bid interest exists. Hopefully (from the conspirators' point of view) other traders will jump on the stock in the hope of getting in ahead of an increase in price. Bid support is considered a form of market manipulation.
Related or Semi-related Video
Finance: What are Ascending and Descendi...2 Views
Finance a la shmoop what are asending and descending tops and triangles well
it's almost like a stock breakout to the good is being squeezed out the end right [Ascending triangle stock prices on a graph]
here... well in this pattern it's like the stock can't help but go up at
the end of the triangles here well ascending tops and triangles is a trading
pattern used by Chartist style traders ie traders who just focus on the graphic
representation of stock performance, well the same holds true for descending tops
and triangles basically take everything we said here and invert it..Oh head rush [Triangle inverted on graph]
there flip that back over - Note the pattern here of ups and downs but as
time progresses the blue line at the bottom acts as if it's a lower limit [Arrow points to blue lower limit line]
where the stock can't bounce through that virtual floor it just goes up and
then one day like as zit that's bursting at the seams well the stock pops and
creates a new set of ascending tops and triangles hopefully it doesn't leave a
pock mark on your portfolio well when it does that [Man holding up portfolio]
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Trading volume is the number of shares trading back and forth at a given time.