Files can of course be used on other materials too - wood, acrylic and wax being the most likely for a jeweller.
A file has a long handle, and then a specific shaped section that has fine, sharp, cutting teeth cut into it.
Standard hand files come most commonly in a flat (rectangular cross section) shape, a half round (D shape cross section, tapering to the tip), and a tapered round shape. Needle files are mini files - usually around 15-20cm long including their handles and these come commonly in a much wider range of cross sections - to reach into small spaces and create specific profiles or edges on your metal.
My top 5 file tips...
1. - Files don't come with handles fitted - this is so that you can choose one that fits best to your hand. Make sure to fit a handle to your hand files before using them - the more comfortably and better you can grip the files, the more efficiently you'll be able to use them
2. - Keep your files clean - use a file brush to remove any filing dust from between the teeth. Use talcum of french chalk on your file before use to help prevent the teeth becoming clogged.
3. - File away from you - start at the top of the file and push away from you, using the full length of the file where possible, for the most effective filing - and make sure your work is supported
4. - If you're starting to collect a tool kit - the most useful files to start with are usually a #2 cut half round file, and a small set of needle files.
5. - To work with wax, wood, or acrylic (perspex) - use a coarse file - a #0 or #00 as these won't clog up as quickly and will be more effective
For more info on files and filing - keep an eye on the Jewellery Club where I'll be loading full notes on this topic in the silver jewellery section later this month...
Images below show a flat hand file, a standard wooden file handle, and a file brush