Here's what is in the Bridge cs5 help pdf file. (I was not able to find this same help info from clicking help in Bridge cs5).
Batch rename files
You can rename files in a group, or batch. When you batch rename files, you can choose the same settings for all the selected files. For other batch-processing tasks, you can use scripts to run automated tasks.
1 Select the files that you want to rename.
2 Choose Tools > Batch Rename.
3 Set the following options:
Destination Folder
Place the renamed files in the same folder, move them to another folder, or place copies in another folder. If you choose to put the renamed files in a different folder, click Browse to select the folder.
New Filenames
Choose elements from the menus and enter text as appropriate to create new filenames. Click the Plus button [+] or Minus button [-] to add or delete elements.
•String Substitution
Allows you to change all or part of a filename to custom text. First, choose what you want to replace: Original Filename replaces the string from the original filename. Intermediate Filename replaces a string that is defined by preceding options in the New Filenames pop-up menus. Use Regular Expression allows you to use regular expressions to find strings based on patterns in filenames. Replace All replaces all substrings that match the pattern in the source string.
Options
Select Preserve Current Filename In XMP Metadata to retain the original filename in the metadata. For Compatibility, select the operating systems with which you want renamed files to be compatible. The current operating system is selected by default, and cannot be deselected.
Preview
One current and new filename appear in the Preview area at the bottom of the Batch Rename dialog box. To see how all selected files will be renamed, click the Preview button.
4 (Optional) Select a preset from the Presets menu to renaming with frequently used naming schemes. To save batch rename settings for reuse, click Save.