A program line is the fundamental entity within Trading Programs that “earns” money. Each program line belongs to a single trading program, which in turn belongs to a single trading partner.
A program line may need to be allocated dimension items from each dimension, depending on the selected mechanism. It is this allocation of dimension items that allows Trading Programs to match transaction lines to program lines, which in turn allows program line earnings to be calculated.
These earnings can be seen when analyzing the trading program for the program line; the analysis page also presents the forecasted earnings and transactions for each program line in the trading program.
You can learn more about program lines here.