What Are They?

Key figures are best thought of as the numerical values in a spreadsheet. Meanwhile the row and column headings are characteristics. Key figures are stored in planning areas and are assigned to them in this transaction.

This transaction shows all of the planning areas. Within the planning areas resides the key figures.

Selecting any of the planning areas will show the key figures.

The Key Figures are added from many available.

Key Figures also can have aggregates in the Planning Area:

Planning Area

Key figures are assigned to a planning area.

http://www.scmfocus.com/sapplanning/2008/01/05/planning-areas/

Make Key Figures Available

If key figures are used in CTM, the key figures must be made available – http://www.scmfocus.com/sapplanning/2009/09/01/ctm-make-key-figures-available/