Two young boys wearing shorts and sandals throw pebbles from a dirt path into a body of water.
Pebbles are being thrown into a body of water by two boys.
Two young boys are boys as part of the description of pebbles being thrown by them.
From a dirt path boys throw pebbles into a body of water.
Sentence 2 summarizes sentence one by restating that the pebbles are being thrown into a body of water by two boys.