The Bulk Rename utility will help you to make rename action of a large number of files or folders to be easier. If you have a few files to rename it is easy to do it manually, but if you have a lot of them, use this tool.
It has a lot of options. For a simple use just enter Match word or characters that you want to be replaced and at Replace put the new word. For example, you can replace all image extensions from .jpg to .png.
In the main interface you will see details for the files that are in current work directory: preview the new name that will be generated (useful before making any changes), type, size, date of creation or last date modified, the length (number of characters) and more. You can sort files by any of these criteria.