"Fair use" is a legal doctrine in the United States that allows for the limited use of copyrighted material without the permission of the copyright owner. When it comes to images on the internet, fair use allows for the use of copyrighted images for certain purposes such as commentary, criticism, news reporting, teaching, scholarship, or research.

Here are some factors that are considered when determining whether the use of an image qualifies as fair use:

Purpose and character of the use: The use of the image should be for a transformative purpose, meaning that it should add new meaning or context to the original work. Non-commercial use is also more likely to be considered fair use.

Nature of the copyrighted work: Fair use is more likely to be allowed for factual or informational works, such as news articles or scientific research.

Amount and substantiality of the portion used: The less of the original work that is used, the more likely it is to be considered fair use. Additionally, if the portion used is not considered the "heart" of the work, it is more likely to be considered fair use.

Effect on the potential market for the copyrighted work: If the use of the image is likely to have a negative impact on the market value of the original work, it is less likely to be considered fair use.

It's important to note that fair use is a legal defense, and whether a particular use of an image qualifies as fair use depends on the specific circumstances of each case. It's always a good idea to seek legal advice before using copyrighted material, especially for commercial purposes.