as in 1st thru 3rd or whatever.

You fellars in AZ. like that question....
www.ar15.com/forums/topic.html?b=1&f=74&t=140696&w=searchPop

Mike

As to the pistol,
1) pebble grip on the grip, no finger grooves.  No accessory rails
2) "grenade checkering" on the front and backstrap, no finger grooves.
3) finger grooves, accessory rails.

There are a few more model specific changes, adding a support pin on some .40 models, etc.  But that's the basics.

Magazines are also by generation, but do not necessarily correspond.

Gen 1 are not fully metal lined (NFML) and are designed not to drop free from the pistol with more than a few rounds in them (how?  they bulge slightly when loaded, why? save partially loaded mags for use when you're almost out).

Gen 2 are Fully Metal Lined (FML), and were designed for the US market, who are used to drop free.  They do not always drop free, and the term "Drop ree" (Df) is sometimes challenged as inaccurate.  

There are of course many other types, LE, post ban 10 rounders, foreign sale only over 10's, etc.      

Thanks, got it. Do the 23s come in all 3 generations?

23's come only in 2 and 3, not 1.  Any 23 will take any 23 mag, 10, 13, LE, export only, fml, nfml.  Also will take any G22 mag, but it will stick out the bottom a bit.  

Hasn't Glock also "ballistically fingerprinted" their US sold firearms in the last year or so after saying that they wouldn't back in 2000?

If I'm wrong, someone correct me.

They don't fingerprint the bullet.  They do participate in the ATf case marking database.  I am unaware of them ever saying they would not.  
If someone has a 3rd gen Glock and leaves a casing behind they can track the gun that fired it to the last legal owner.    

Quoted: You fellars in AZ. like that question.... www.ar15.com/forums/topic.html?b=1&f=74&t=140696&w=searchPop

...and here www.ar15.com/forums/topic.html?b=5&f=13&t=2046