Yield sign
Slow down and give the right of way to traffic and pedestrians already in or approaching the intersection. Stop only if you need to.
How to recognise it
This sign is a downward pointing triangle in white, the standard background for a rule you must obey. These carry the force of law. Ignore one and you have broken a traffic rule, not just a guideline. Most are white rectangles with black text, and the handful that are not, the stop and yield signs, get their own unmistakable shapes.
What the test wants you to know
The downward triangle is used for nothing else. The distinction examiners test is that a yield does not require a stop when the way is clear, while a stop sign always does.
The sign people confuse it with
Yield gets mixed up with Stop more than any other pairing in this category. Put them side by side and the difference is obvious, which is exactly why it is worth doing once rather than meeting them cold in the exam.
Practise it
Reading about a sign is not the same as recognising it in half a second with an examiner watching. Every state road signs test on this site shows the sign and asks you to name it, then shows four faces and asks you to pick the right one.