Administrative note{insert definition here}
AvailabilityOn the item record - may describe information about where an item is (available; recently returned) or if it can be circulated. As of Q12020 labeled as "Item Status"

Container records hold multiple Instance, Holdings, and/or Item records and serve as virtual containers.

The container represent an additional level of hierarchy and associate data that may not have bibliographic associations. The container is not yet implemented as of 3/27/2020.

Effective call numberThe string that displays in apps other than Inventory as "call number." This is stored at the Item level and takes data from either the holdings or the item record call number field. The effective call number includes the prefix, call number, suffix, volume, enumeration, chronology, and copy number.
Effective locationThis is currently an item-level property. FOLIO has permanent and temporary location fields on the Holdings and Items records. There is built-in logic for FOLIO to compute the item's "effective location" based off of what values are set. See Holdings and Items Effective Location Logic in FOLIO in the Resource Access wiki for more details.
FormatA combination of MARC fields 337 and 338. Can be used to filter search results.
HoldingsThe Holdings record contains data about the materials held, such as location and call number. A Holdings record must be associated with an Instance record.

The Instance record is what is known the bibliographic record (or bib record, for short).

The use of the terminology is inspired by the BibFrame universe (Instance, holdings, and items).

InventoryInventory is the FOLIO app that stores bibliographic, holdings, and item data in the form of Instance, Holdings, Item, and Container (not yet implemented) records. Instance records may be created within FOLIO or generated from records in source record storage (SRS).
ItemThe Item record contains data specific to a single volume or piece, such as barcode and circulation status. An Item record must be associated with a Holdings record.
Item Status

Item Status is a field that reflects information about an item's availability, staff processing, and needs for future use.

See Item State in FOLIO for a discussion of the three-part item state structure - which is currently in development.

Loan typeLoan type is a field on the item record that can be used as an element in FOLIO circulation rules

Items must have a permanent loan type. They can also have a temporary loan type. If an item has a temporary loan type set, that is the loan type that would be matched on in circulation rules.
Mode of Issuance
MoveMoving a record changes its hierarchical association. A holdings record is moved from one Instance to another. An item is moved from one Holdings to another.
Nature of Content
Needed ForOn the item record; Allows libraries to assign a path for an item to follow when it is needed for specific things. These may be for staff needs, or for patron needs. Needed For might include Requests; Course Reserves; Binding; etc. As of Q12020 not yet implemented. See Item State in FOLIO for more information.
ProcessOn the item record; Describes a staff process that an item is in. Processes might include Digitization; Repair; Cataloging; etc. As of Q12020 not yet implemented. See Item State in FOLIO for more information.
quickMARCA lightweight editor for updating MARC records in SRS and pushing the corresponding changes to Inventory Instance records.
Reference dataData that are referred to by other records in the system. Examples include instance Formats and Resource types.
ReorderReordering a record changes the order in which it displays but does not change its underlying hierarchical association.
SRSSource Record Storage. If an instance has an underlying MARC record, then this record is stored in SRS. The underlying MARC record is also named the source of truth. 
Staff SuppressAllows a record to be suppressed from some staff based on permissions. Use depends on local workflows and needs.
Statistical code
View sourceView source means view the underlying bibliographic record, from which the instance record origins. View source can point to a MARC record in SRS internally in FOLIO, or direct outside of FOLIO if the library use a union catalogue as source of truth (e.g. LIBRIS and K10Plus).