First edition, OK, I’ve got that. But when the number line has a 1 in it, is that first printing? First impression? First state? Some I’ve seen actually say “second impression”–how is that different from second printing? 
On BBerry so must be brief. There is NO rule - buy the Guide to Identifying Firsts, the add specifice research for that title.
From a lingo standpoint, “First Edition/Printing/Impression” typically are used interchangeably. State refers to differences within a First Edition print run due ANY differentiating factors - assignment of “state” is made by dealers and collectors after the fact…
So my mental picture is that some guy in the print shop notices that the “e” on one page is smushed so he replaces that one piece of type with a good one and now we have the “second state” printing–even tho’ it might be the same print run. And collectors go nutz looking for a copy with the smushed “e” no doubt. Rather like the stamp with the upside down plane.
Although I’m having a good time “collecting” I’m not at the point where I’m going to buy a guide to determine which editions are which. I’m happy any time I get a complete number line, 'cause I can up the sale price on those. On my personal bookshelf I keep the later ones so I can read them in the tub. 
Yep - that’s it. Errors, changes in appearance (the color of the binding cloth, or a change in business language on the c’right pagean etc). Prices/values can vary a lot due to states depending on the title…
OK, so I have a number line that says:
02 03 04 05 06 */RRD 10 9 8 7 6 5 4 3 2 1
First edition, first printing?
The asterisk is a little graphic thing, four diamonds in a diamond pattern.
No clue - you have to check on THAT publisher’s rules. Not sure if the numbers starting wih 0 are years, major print runs or something else (by major print run, I mean when they use up all the numbers in the countdown, they often put an 02 or a B somplace close to indicate that the countdown is for the second run…)
I can’t think of a single example in which the 02 03 etc. aren’t years.
The norm for most publishers is that in a 1 through 10 listing, the 1 means first printing. That’s essentially universal today. There may be some examples where a 1 is maintained on a book club edition, but that would be an oddity. Unless you know of a reason to exclude this as a first you can list it as a first. Almost anything that uses a number line of that sort is so new that guides probably wouldn’t help you. They’ve only been standard for a few years.
Unless you are getting into extremely high end and specialized sales, ignore states. First editions are important and that’s about it. If it’s not a stated first then you need to do research into how a publisher listed first editions. Impressions and printings are interchangeable.
To expand a little on the sales of common books, just remember that every book ever published has a First Edition. Most don’t get a second, and most should not have gotten a first, either.
Being a First/First does not magically add value to a given title. If you happen to have the Frist/First of an early work by an author who has gone on to bigger things, you may have something of value. But the resale value of most recent fiction is not enhanced by your copy being a First Edition.
In most ways, you are correct. But publishers find ways around that - if the first printing of a Stephen King novel is 1 million or more, then yeah, that first edition will likely never hold much value. But there are still errors - look at what happened with Franzen’s The Corrections, when it got hyped as an Oprah book/then not, and there was a First State due to the inclusion of an errata slip at the beginning of the print run. And there are limited editions - most top authors have tiered levels of LE’s - 100 copies signed and bound fancy; 500 copies unsigned, etc. And there are errors in LE’s - the UK Collector’s Edition of Azkaban lists Joanne Rowling (on the copyright page as the writer attribution), later modified to J.K.