MAN: Just because I find content on the internet does not mean that I'm necessarily allowed to use it for free. If I were doing a research paper on whales, for example, and searched for whales, and go to the image results, you can see that several pictures appear. In order to find pictures that I'm allowed to use, I can click on Tools and Usage Rights. 

As you can see, by default these images are not filtered by a license, meaning that some fall under copyright restrictions. Labeled for use with modification means that any pictures can be used and modified. Labeled for reuse means that I can use the images, but I can't take them out of their original context or edit them. 

Labeled for noncommercial reuse modification means that I may use the images and modify them or edit them, however it has to be for a noncommercial or nonprofit use. Labeled for noncommercial reuse means that I may use it for a noncommercial use. However, it cannot be taken out of context or edited. 

The safest choice to use is labeled for reuse with modification, because this means that you are protected for both commercial and noncommercial uses of the images, and can edit them in any way. By selecting this option, all the pictures that appear are safe for me to use legally in my documents or presentations.