Every team concept lives in one place, on the Settings › Team Management page: how many people your account has room for, who holds which role, and which invitations are still pending.
Seats
A seat is one person your company can host on the platform. The count appears at the top of the Team Management page as the line "{used} / {total} seats used".
Pending invitations occupy seats too: when you send someone an invitation, the seat is reserved before that person accepts. In other words, the counter shows the total of "members on the team + pending invitations".
When all seats are taken
Once the used figure reaches the total, the Invite button is disabled and you see this warning: "All seats are taken. Upgrade your plan or free a seat to invite a new member."
There are two ways to free up room: remove a member from the team with the Remove member button marked by the trash icon, or withdraw a pending invitation with Cancel invite. The warning also points to a plan upgrade; note, however, that your seat count does not currently change on its own based on your plan selection.
Owner
The Owner is the holder of the company account. Team management actions — sending invitations, changing roles, removing members — are concentrated with the Owner. The Owner role cannot be granted by invitation; the invitation list offers only Manager and Member. If an invitation you send is refused on permission grounds, the warning "You are not authorized to perform this action." appears beneath the invitation box.
Manager
The Manager sits one level below the Owner on the team, and the role can be assigned by invitation.
Member
The Member is the standard team member, and it is the default role pre-selected when you send an invitation.
Changing a role
On the Team Management page you update a person's role from the Change role list next to that member. This list and the Remove member button are visible only to the Owner; if you do not have the permission, these controls do not appear on screen at all. The Owner's own row cannot have its role changed, and the Owner cannot be removed from the team.
Do not confuse this with the role in conversations
An Owner badge may also appear next to a person's name in the Participants list of a demand conversation. That badge marks the principal counterpart on the buyer side and the supplier side of the conversation; it is a separate matter from your team role within your company. Teammates added to a conversation later do not carry this badge. Adding a teammate to a conversation does not consume a seat — seats are only for the people you bring into your company team.