Individual trading halts only affect a particular stock and temporarily freeze trading on the exchange that the security is listed on, rather than affecting the entire market.
Individual halts will normally last less than 1 hour but may last longer. These halts can occur multiple times in a single trading day or remain in place over multiple days in certain instances. If a given security is halted during the last 10 minutes of normal trading hours, the primary listing exchange will not reopen trading for that security until the next trading day.
Individual stock halts can be initiated for news, regulatory reasons, or volatility.