The halt, which can happen a few times a day per security if FINRA deems it, usually lasts for one hour, but is not limited to that.
The halt in trading for the affected security gives investors time to review the news and assess its impact.
Another situation in which a trading halt might occur is when the exchange is uncertain "whether the security continues to meet the market’s listing standards.
[1] The NASDAQ and other exchanges currently use 11 codes to specify in more detail why trading has been halted for a security.
[3] A "non-regulatory" trading halt occurs if "significant order imbalance between buyers and sellers in a security" exist.