Actually I think it's about a map, as in, planetary chart.

You "use" some items in the inventory by pressing E while mousing over them, but it only works when the "tooltip card" of the item is visible (it should list your options, including "E to use").

It's a bit buggy, still, though. I don't know why they have E both change tabs, and "use" items at the same time. Frequently, the game doesn't use the item but changes tabs instead. Same thing with re-organizing your tech, by pressing E to pick it up, it tends to also switch tabs while picking the tech up. On controllers, this doesn't happen, because it's two different buttons on there - and you could re-bind the controls on PC to solve that issue until they worked that out, too.

But yeah - it's annoying.