Toxicodendron radicans, the poisonous spready plant with hairy stems (seriously, that’s the Latin translation), also known as poison ivy. Yes, it has been written about in this blog before, but this plant is pure evil. If you are east of the Rockies in the United States, make sure you can id it. And leave it alone. And buy some Tecnu. And some calamine lotion. Just be prepared.
So-three leaves. On a vine. Which can be toothed:
Or smooth edged:
It can be on the ground or reach out to slice your face while hanging from a tree. But the leaves are a bit less useful than having a good idea of the stems, which are varying degrees of red, regardless of the leaves being present.
So got that? RED STEMS. Three leaves, and RED STEMS. Also look up, it might be above you.