What does 'WIP' mean and what are 'WIP' units?

WIP stands for Work in Progress.   WIP units would be units that are in the process of being consumed by the Build feature.

We have a Build feature where you can create a "Finished Good" product id from a bill of material(BOM) list of items that are "component" items(product ids).

IF you had a finished good product id called: HAND-CREAM-01

and the HAND-CREAM-01 had a Bill of Material(BOM) list of these component/raw material items(product ids):

When you wanted to make some of the HAND-CREAM-01, you would need to consume the BOM items from inventory in the ratio defined by the BOM.

When you begin a Build, the component items(product ids) from the BOM of the "Finished Good" item will be moved to WIP until the build is complete. When the build is completed the finished good product id stock will go up and the component stock levels will move from WIP to decremented from stock at their current sublocation.

Our WIP means "Work in Progress", the raw materials being consumed, and NOT WIP as in "Work in Process", which normally represents the partiality completely "Finished Goods" items being manufactured or "Built."