What is a Call on Tribes?

A Call is a market idea shared with a Tribe: the asset, the direction, the thinking behind it, and optionally a target, a stop or a time horizon. It is a signal, not an order. The person making it does not have to put money behind it, and nobody who reads it is committed to anything.

A Call is not a Trade

The two are separate objects on purpose. A Call is the idea. A Trade is what happens when one or more members actually execute. A Call can exist with no execution behind it at all, because a member may be a good scanner without having capital free at that moment.

Why they are measured separately

Because they answer different questions. Call performance asks whether the signal reached what it said it would, independently of who traded it. Trading performance asks what participants actually made or lost. Keeping them apart is what lets a Tribe tell a good analyst from a lucky one.

Who can make one

That is a permission rather than a role. Tribes can allow every member to post community Calls while restricting official Calls to members with a Caller or Analyst permission, which is what keeps a large Tribe's timeline usable.