A watermark is a semi-transparent image that overlays the image itself. Unlike the other types of image protection that we have discussed, the watermark is actually embedded into the image itself.
A watermark in the image doesn't stop someone from taking your images. It is impossible to do that. However if they do steal watermarked images then those images are still watermarked. The watermark is extremely easy to insert into an image but extremely difficult to remove without significantly damaging the part of the image overlaid by the watermark.
Anyone who steals your images will therefore either have to use them with the watermark still in place or will have to put almost as much effort into removing the watermark as would have been required to draw the image in the first place - something that they are unlikely to do.
Provided that you place the watermark so that it covers a significant portion of the image then anyone taking the image is unlikely to have the ability to remove it.
The watermark can actually be just about anything. It might contain your special logo and some text. The text can identify that the image is copyright, it might also identify who the image belongs to.
One text watermark that you could use is the address of your web site where the images appear. This makes it obvious to anyone who views the images anywhere else that they have been copied from your site. The most that the person who stole the images could do would be to post some sort of notice on their page stating that they have your permission to display the images (even though they don't really). Of course these images are now working FOR YOU because anyone who sees the stolen images now knows where to find your site. The thief is providing you with free advertising.
Of course you will still want to get the thief's site shut down once you find out about it. Having a watermark in the image will make this easier too since the images are readily identifiable as yours so the thief can't claim that they own the images.
So how do you apply a watermark to your images? Well you do that in your graphics program by editing the images themselves. How you do it depends on which graphics program that you have.
