Bears & Bulls
When things are going well for a sustained period of time in the stock market, it is often described as being a "Bull" or "Bullish" market. This means that there are a lot more stock prices rising than falling, and that investors are feeling confident that this trend is likely to continue.
When things are going poorly, it is often described as being a "Bear" or "Bearish" market. This means that there are a lot more stock prices falling rather than rising, and that investors are more pessimistic.
When the number of stocks rising and falling are about the same, the market is called "Mixed".
There is no established formuia for defining a market as "bull", "bear", or "mixed".
These terms can also be used to describe feelings. If someone is optimistic about a company (even if the market is doing very poorly), they might say that they are "bullish" on a given stock.
These terms can also describe sectors of the market. For example, the overall trend might be doing poorly (bear), while technology stocks are doing well (bull).
Legend has it that these were chosen based on how the two animals attack. A bull thrusts its horns upward, while a bear swipes its paws downwards.