In many places long standing brands often take the name for a type of tool. For instance, someone will say “can you pass me that Skil saw?” And the brand be a DeWalt. Same thing with “crescent wrench”. Crescent is the brand of tools that was either a patent holder or major contribution to the tools wide spread use (aside from the fact it's a useful tool). The actual name for a “Skilsaw” is a “Circular Saw” so there is no difference between a Skil saw circular saw and any other circular saw. That's not to say there aren't other “types” of circular saws like many of the people mentioned in their answers. But,, Unless of course your asking for a “Skil” brand saw of another type, like a Skil reciprocating saw. Whats commonly referred to as a Skil saw and the general term “circular saw” are the same thing. But, with any other saw type, like the reciprocating saw, you should probably just ask for the reciprocating saw or “Sawsall” (because the reciprocating saw saws all sorts of things). And in case your wondering. The actual name for the “crescent wrench” is “adjustable wrench” or “adjustable Spanner". You may find it interesting how many things are commonly called something based off brand recognition, to the point of it actually being thought that's the actual name of something. The Phillips screwdriver and screw were patented as a “recessed cruciform screw” and got it's name due to a person who pushed for it's widespread use I believe in the 30’s The “Allen wrench” is actually a “Hex wrench”. These are just a couple examples of what I mean. It's not just tools, either. Just more common in tools. Another funny play on words. Did you know the term “hot water heater”, though I'm not sure if that term is used anywhere else, but it's used allot in the South. Is incorrect? Why would you heat already hot water? It's actually a “water heater”. But pay attention, you may be surprised how many people say “hot water heater” and may be surprised to realize you have said or do say it yourself without realizing it. But don't feel dumb if you use the term “Hot water heater” because I actually Argued once that water can still be heated even though it's hot, and due to the fact the “water heater”will most often increase the temp of already heated water (to sustain desired temp as it drops below temp setting) rather than the few times it would heat cool water making it hot, that the term hot water heater was actually correct. But as I was being difficult intentionally, when I was told to shut up I simply smiled and dropped the argument there, as essentially, both would be correct.