A picture's dimension is determined by several values. One of them is the Image Width. Together with image height, it delivers information about the actual size of a picture, photo or image. This size should not be confused with the file size of the image file.
The value of Image With is typically given in pixel. Some graphics or image viewing programs allow different values as well, such as inches, mm or cm. A direct conversion can be difficult though since the pixel value only roughly represents the inch or mm value it is translated into.
When printing, uploading or embedding an image, the Image Width can play a crucial role. Often times, image uploads are limited not only to a certain file size but also to a certain image dimension. Also, when planning on embedding an image in a document or video, knowing the actual width will help to avoid black bars or crooked formatting.