Inbox
The Inbox is where new Stories (and Issues/Ideas or impediments/improvements) are put when created from the main menu.
User
A user can have different site and circle access right which will determine what they can or cannot do.
User Invite
Users are invited by email. The user invite specifies the roles and/or team memberships of the user.
Preplanned List
A Preplanned list is an ordered list of product backlog items that are yet to be explicitly planned. Preplanning stories/epics is to obtain an early grouping of items for a future release.
Team
A team is a collection of users. A team can be mentioned in comments and assigned to tasks.
Site
A site is an organization account.
Milestone
The milestone specifies a deadline. Epics and stories can be linked to this milestone to indicate that they must meet the deadline.
Sprint
A Sprint is a time-box during which a “Done”, useable, and potentially releasable product/service increment is created.
Release
A Release is a special type of Milestone. It is the base for the planning in the Product Backlog.
Circle
A circle is a unit within the organization containing one roadmap and one product backlog.