As for the other, they are used to precipitate and wash DNA. Usually if you use isopropanol, you do not need 95% ethanol since they both serve for the precipitation. 70% ethanol is just a washing solution that will not resolubilize DNA, but still rinse out the Acetate
TE is TRis EDTA. Tris is a buffer, EDTA is an chelator for divalent cations. Since many DNAse use metallic cations (Mg2+ etc..) as coenzyme, if they are chelated, they will not be able to degrade your DNA during extraction.