This is for removing or changing characters or strings that might otherwise end up in the variables you're trying to fill. With the exception of spaces that have been changed to periods or underscores, such things are not commonly found in the middle of a string that has been properly isolated (e.g., "CD#" is unlikely to be found in the middle of Title). But it is a handy tool when the circumstance arises.
An example: It's not uncommon for a title to include a colon (":"). Colons are illegal in filenames, however, so they're usually replaced with a hyphen ("-"). Find and replace can be used to change these back into colons (e.g., The Title of 2001 - A Space Odyssey (1968).avi becomes 2001: A Space Odyssey).
