From TEXAS...
ICE = 4methylaminorex. Always. Period. Not the same as methamphetamine
Glass = High quality (shards usually) of methamphetamine crystal
Crystal = Slightly lower quality than 'glass', but still meth
Tweek = any meth (but not ice), but usually refers to low grade brownish icky gummy stuff.
Peanut Butter = the usual, low grade crap meth. Looks only slightly better than its name
Crank = not meth. something 'similar' usually made in a homebrew thing that uses household precursors and does NOT result in actual meth (though most people would like you to believe they can make meth from shit around the house...)
Dex = dex-amphetamine (ritalin, adderall, not always actual DEX, but more commonly just an 'upper-pill')
Speed = no one uses that term (would refer to amphetamine, not meth)