A 'tippet' is a rather minor word of advice!
Most people will refer to the tippet as the section of line they use between fly line and fly.
Many will also refer to this as the leader.
I often refer to the long piece of line that you attach to the end of your fly line as the leader and the end to which you tie the fly as the tippet.
You can purchase purpose built tapered leaders which, as the name suggests, is a length of clear/ish nylon that has a larger diameter at the 'butt' section (attached to the fly line) and gradualy thins down towards then end to which you can then tie another length of tippet and then tie your fly on the end of that!
Ben