The master parks his horse for a few hours so it can CHEW grass.
駐 (stop at) + 車 (car) + 場 (place)
= 駐車場 (parking lot.)
parking lot. Interestingly, there is no word for 'parking space,' in the sense of "Keep a lookout for a good space!"
駐 (stop at) + 車 (car) + 禁止 (forbidden)
= 駐車禁止 (no parking)