whats the diff?

Hello to all here! I need the answer to a question. What's the difference between a plasma cutter and a tig welder? I've seen the word "inverter" associated with both. Does this imply that they both are somewhat the same? I would like to buy a plasma cutter but the high cost is stopping me. If I could buy a plasma cutter and use it for tig welding also the cost would become a little easier to swallow. Sorry if this is rehashing old stuff.:banghead: