Plain English Meaning
Yellow signs at a taxiway intersection that tell you which taxiway is which, with arrows pointing the way to turn to get onto each one.
Full Definition
Airport signs with a yellow background and black inscription that identify the designation of an intersecting taxiway leading out of an intersection, with an arrow showing the direction to turn to reach that taxiway.
Context Anchor
Seen while taxiing on the ground, especially as you approach a taxiway intersection.
Why Pilots Care
They reduce the chance of wrong turns that could lead to runway incursions or delays.
Analogy
Like highway exit signs that tell drivers which lane or ramp to take next.