Photo Hosting: A site that allows anyone to share photos on the web. These sites store the photos, however this is not a permanant place for your photos. A backup of all photos placed on the site should be a disc, thumb drive or other permanant storage device. 

Most photo hosting sites are free.

Photos are filed in Albums.

Photos can be sorted by Person, Tag, or Location. This allows searchs for specific people, places, or things easier.

Some Photo Hosting Sites let you edit photos, create pages to go with photos.

Most Photo Hosting Sites sell services such as; printing your photos in different sizes, creating coffee table photo books,  mugs, totes and tee-shirts using your photos.

These web sites allow others that have access to your online albums to download, or order any of your photos. So, Aunt Jane can get exactly which photos of Joe's 2nd birthday she wants.

Here are photo hosting sites where you might want to host your photos.

http://postimage.org/ 

http://picasa.google.com/ (Google Picasa is discontinued)

http://www.shutterfly.com/

https://www.smugmug.com/

http://www.snapfish.com/

http://www.photoworks.com/

http://photobucket.com/

http://www.kodakgallery.com/ 

http://www.wikialbums.com/

http://www.amazon.com/clouddrive

http://www.onedrive.com/

http://www.dropbox.com/

http://explore.live.com/windows-live-essentials-photo-gallery-get-started?os=mac

Windows Live Essentials has a photo hosting component