For the most part, different fuse types denote differing mounting/connection styles. Fuse trip characteristics (speed of trip on over current, arc containment, etc) also come into different fuse designations.
ETA: A Type T fuse is rated for 20000 amp current capacity, but isn't rated for DC voltage. This means that the fuse body will contain a 20000 amp short, without bursting or burning. This rating is only valid for an AC circuit, and no ratings are published for DC circuits.