The filepath is arguably the most important part. It's the unique identifier for each file, and is what everything uses when referring to files.
The format is very similar to that of *nix-style paths; the root directory is the file storage directory for the installed system and it's just directories and a filename at the end after that. Nothing special, really.
The filepath is case-insensitive; when they're processed, they're reduced to lowercase and all extra slashes are trimmed out, and ones are added in the correct places if needed. Also note that using . or .. is not supported. It may get the right file, but it will confuse the ACL and file tables.