Lane Ends sign
The road narrows ahead and one lane will disappear. Merge early into the continuing lane.
How to recognise it
This sign is a diamond stood on its point in yellow, the warning colour. Yellow diamonds telling you what the road is about to do. They are advisory rather than mandatory, but ignoring them is how people end up in ditches and how examiners end up failing you.
What the test wants you to know
The difference from a merge sign is whose lane vanishes. Here yours might be the one ending, so the safe move is to adjust before the taper rather than racing to the front of it.
The sign people confuse it with
Lane Ends gets mixed up with Merge 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.