This is market participant who believes that market prices will rise in the near future. Overall, this speculator (trader or investor), which "is bullish," opens a deal to buy, taking the bull by the horns, to help prices to rise. If the "bulls" are very active on the market we call such a situation the "bull market" (see). There is an opinion among traders, that bulls have long tails, so the position on the purchase is called "long" (see). Details about how these two categories of traders interact on the financial market can be found in the book “Bulls, bears and millionaires: war stories of trading life” by Robert Koppel.