Enterprise plans include a fixed number of seats, letting you invite teammates to share your organization's survey limits instead of each person needing their own subscription.
From your Team page, send an invite by email. Once accepted, that person becomes a member of your organization and their surveys count against your shared plan limits. You can promote trusted members to Admin, which lets them manage billing and invite others alongside you.
Remove a member at any time to free up their seat, or leave a team you've joined if you're no longer part of it (the team owner can't leave their own team - ownership would need to transfer first).