"Metadata" is additional information included in a file. Mainly, JPG files created by many digital cameras, mobile phones, etc store additional information about the file in JPG metada. Most of you are unaware of such a thing.
A metadata can contain many information, like the model and company of the camera, copyright information, title, rating, subject, tags, comments, etc. It can contain distance of the camera from focus, adjustment of the lens, exposure time. It may even contain GPS information, serial number of the camera and/or the program used to edit the picture, and a thumbnail of the original picture and many more.
So, an image may be a little bit bigger than it really should be. Many of you might need to change or remove these information for reducing the file size or removing sensitive information.
Microsoft Pro Photo Tools is the best one you can get to do this. It has got options for editing all kinds of metadata information.
One cool feature is a world map to locate and add/change GPS information of the images. It has even got 3D map view and bird's eye view and search options to easily locate a place on Earth.
Size of image thumbnail can be changed to maintain the file size.
And best of all, you can rate your favorite picture in 5 stars.