Segment is usually represented by requirement for producing legal reporting statements based on different product groups or services which the company is providing. Usually Profit Centers area assigned to Segments you are able to group them as such. In Some cases you will be able to use profit center groups instead of segments to get the same result, but in case you want to have profit centers pointing to one segment from different profit center groups, then Segment is the way to go. There is also a possibility to implement custom derivation of Segment based on Business Add-In (BADI).
IMG Path: Enterprise Structure -> Definition -> Financial Accounting -> Define Segment
When you enter in the transaction, click on “New Entries” to create new Segment.
Enter the name and Description and hit the Save button.