I play marth.. and I have no idea what drifting and dash / float / WD back abuse is...
That might be the single saddest statement I've ever seen on SmashBoards... This community is clearly not doing its due diligence when it comes to educating players about the basics.
1.
Dash dancing: alternating dashes left and right; if a player SHFFLs at you, you can often dash away and then dash back towards them and grab them as they land (or punish with other stuff)
2.
Drifting: when airborne, you can control which direction your character goes slightly; some characters have more aerial control than others (Jigglypuff has ridiculously good aerial control so she can attack opponents with an aerial and then drift/weave back out of their range to avoid counterattacks)
3.
Wavedash (WD) back: similar to dash dancing, WDing back allows you to avoid approaches from the opponent and quickly counterattack; dashing forward frequently precedes a WD back so that your forward movement scares the opponent into doing something and your backward movement keeps you safe until the move or w/e they did impulsively is over and you can punish