Every time a scheduled query is executed, there is a check for an Alert status. 

Currently, there are three status types for an Alert:

• TRIGGERED: This means that the condition you set for the alert met the conditions and the alert is on. Suppose you have a table that tracks logins to your API, and you set an alert on distinct_user_logins_per_hour > 100. If the query returns 105 logins per hour, for example, the alert will be triggered, and you will receive a notification through the channel you chose.
• OK: This means that the condition you set is either not met. This can happen both before the alert goes into the TRIGGERED state or after. In this example, we have it in the TRIGGERED state. Suppose the value of distinct_user_logins_per_hour changes to 70 – the alert will move from the TRIGGERED status to OK.
• UNKNOWN: This means that the query your alert is set for hasn't run yet. You can run the query manually to enforce the alert to check the conditions (not a must, since alerts work on scheduled queries. Eventually, it will run and check its status by itself).