What did the line of demarcation show .the land of the maya's and the aztecs .where water from rivers flow into the atlantic ocean or the pacific ocean . where portugal and spain could settle and trade . where central america ends and south america begins

The land of demarcation was a line approved by the Pope Alexander VI at the treaty of Tordesillas, in which Portugal und Spain "split" the world into two parts: everything  west of the line that was either discovered or about to be discovered would be under Spanish contror; east - Portuguese control. (c).

(the line was moved a bit to the west in 1494, which resulted in brazil belonging to Portugal- but this was before the official discovery of Brazil: this suggests the Portuguese had knowledge of Brazil earlier than claimed! (1500)