Advantages: Reasonable storage size for free
Disadvantages: For the unwary your images can be used by others
Flickr is an online photo sharing community. Now I need to use the term 'sharing' carefully here. I mean sharing in the sense that you can upload you images to Flickr in order that others can see them (and if YOU wish, others can use them). Many people take this too literally and feel that if they need an image to use anywhere, they can just lift it from Flickr.
Flickr allows you to control to a degree who sees your images and also gives you the opportunity to state whether you wish to let others use your images. You can allow, depending on your settings for friends, family or anyone to see your images and likewise you have similar controls as to the size of image which can be downloaded. The 'traditional method' of saving images from the net can be blocked, although this can be circumvented (naughty) for only the smallest size of image.
You can state on each images page whether All Rights Reserved on the image i.e. you own the copyright and don't wish for others to use the image without your permission. You can also state whether you will allow the image to be used under the Creative Commons idea, whereby others can use your image within limits, as long as you are given a byeline.
Flickr is actually a great online community, in the first instance for those interested in photography, but there are also groups for practically any subject for people to join and discuss, although the main emphasis should be on adding photos to the group around which the group revolves. So if your group is about Architecture, you add pictures of buildings.
Flickr is also a stepping stone for photographers to have their work seen and their talents recognised, and at its everyday level a good place for you to upload photos you want your friends and family to see, but note that should you want to upload more than 200 images you will need a pro account at an annual cost of around $25.
Summary: Reasonable good image sharing website