At the attendance query you are able to ask your members to confirm their participation for an event, like ESL ONE Cologne or DreamHack Winter or anything else.

The first step is to create a new event. Then mark the checkbox "Members have to confirm participation", like shown at the screenshot above. After this, send invites to the members you want to query their attendance for your event.

The selected users will get notified by email (if the address is filled out in the users profile). The invited members are now able to accept or decline the date of your event.
You also see when the first and the last reaction of each user happens,