RE: new guy A " HALT" may be called for by the listed company or by the trade commission.It is a period of time during which there will be no trading in that listed stock.
A company may ask for a halt because they want to issue a news release and to attempt to give notice to all shareholders during the halt period.
The trade commission may call a halt if it is suspected that there is unusual trading of if there is some leaked information not known to the shareholders for instance....