There are a number of different status's which can be set for someone within a roster;
Standby
Used in instances where someone is waiting & ready to be rostered, but hasn't yet been officially given the go-ahead to attend the event.
Contacted
Used to indicate someone has been contacted to attend an event, but not yet responded or confirmed they are able to attend. Generally used in conjunction with notes which are entered indicating the latest contact someone had with the person.
Tentative
Used to roster someone to the event, but are still awaiting confirmation from the person that they are able to attend. The person rostered can confirm themselves via the home page and also when viewing the event details.
If they are still 'Tentative' within a week before the event, an SMS message is also sent to them a week prior to the event to ask that they confirm if they are able to attend the event.
Confirmed