Approximately every 90-days each publicly traded company reports their financials to the Security Exchange Commission (for US companies or the equivalent for non US companies). These financial reports are better known as their "earnings report" and when the companies are releasing the reports stock analysis call it "earnings season".
During earnings season, there is a level of uncertainty in the market. Investors and analysis will use the guidance number to judge how a company is going to perform over the next three months. 90-days later, when the next earnings reports is released, the company will be judged upon these expectations and whether it beats, misses, or matches the guidance. A company could generate high revenue, profit and perform well but still receive a negative hit because it didn't beat its guidance. This is referred to as a "mixed report".
While some volatility is to be expected, sometimes there is unexplained volatility on poor or mixed reports. Read my report on what causes major volatility during earnings season to see why I believe this happens.
Remember that Mr. Market is always correct, but what is correct today is not always what is correct tomorrow.