In most OLAP tools, Elements are the components that make up a dimension. For example in a Month dimension you would likely have elements January through December. You might also have consolidated elements such as "Q1" and "All months" that consolidate the values stored in the children.
In ODBO interfaces, Elements may be referred to as "Members".
SAP BW Terms Vs TM1 Terms
The terminology used by SAP Business Warehouse (SAP BW) varies from that of other tools like TM1. "Characteristics" are the equivalent of dimensions in TM1, with the "Key Figures" characteristic being the equivalent of the measures dimension in TM1. "Characteristic Values" are the equivalent of a TM1 element.
(Reference: TM1 TurboIntgerator Guide (version 9.1) Chapter 3, Analogous Objects in SAP and TM1.)