This name is used for woods from at least a dozen different genera, so it's pretty much meaningless.
What I BELIEVE I show below is a South American wood that is used almost exclusively for flooring and heavy construction (dock pilings, etc.).
In the USA, if you see the name greenheart, there is a good chance that it refers to ipe, but that's certainly not necessarily the case.
both sides of a plank and a closeup. These are from the BogusColorVendor so the colors are unlikely
planks listed as greenheart / Cholorocardium rodiei
plank listed as greenheart / Ocotea rodiaei (a synonym for Cholorocardium rodiei)
plank listed as greenheart / Tecoma chrysantha
flooring --- you would think that the flooring people would have figured out that apparently using nails in this wood causes stains to spread in the wood.
bowls by Bryan Nelson (NelsonWood). Bryan fine-polishes his bowls with 1200 or even higher grit sandpaper while they are spinning at high speed on the lathe and then finishes them there with a friction polish of his own devising, thus achieving a shine and color vibrancy that is beautiful to behold.