Stock photos is a supply of images that are licensed for specific purposes.
using images you find on Google might violate copyright law
there are plenty of free stock photo sites, so you shouldn’t have to pay money for good images
Suggested Tools
Pixabay (email login or Google account login required) - images uploaded by professional photographers that are free to use
Public Domain Pictures (email required for login) - free and premium subscription to stock photos
Photos for Class (no login required) - safe G rated photos to download
Pics for Learning (no login required) - safe photos to download or save to Drive
Morgue File (no login required) - free photo archive
Google Images (no login required) - when searching for images you must change the usage rights to 'labeled for reuse' or 'labeled for noncommercial reuse' (video demonstration)
Cupcake (no login required) - free photos by photographer Jonas Nilsson Lee. The images are many nature theme.