If you didn’t drive through a puddle, rain, or wash the bay, it’s probably leaking.
stick your nose near it and take a smell. Does it smell a bit sweet? That’s coolant if it does. Stop breathing it in, it’s not good for you.
if it has plastic tanks, check to see if coolant is pooling around where they meet the metal rad. Also check top and bottom hoses for leaks, and the rad cap.
And never take off the cap when it’s hot!!!