The tgz at the end of the filename indicates it's a zipped tarball, a compressed file. You need to uncompress it before you can do anything else with it. You can probably do this by right clicking on it and selecting an option from the context menu. There's probably one called 'Expand' or something like that. Or at a command prompt you can do
$ tar xvf 'iP100 Debian Linux driver tgz'
Notice the quotes around the filename because it has spaces in it. (Does the filename really have spaces? They usually don't, but the way you've written it it has.)
What you do once you've uncompressed the file depends on what you end up with.
It will probably help if you tell us what version of Linux you are using. It may also help if you can tell us exactly what you downloaded and from where.