Okay, just to give an idea of my current understanding. Reforming is a step one can do after one has cracked some hydrocarbons. As such, the process of reforming is dependent on a separate process, cracking. What it involves is cracking the hydrocarbons, then putting them together in new ways, whilst still having the same chemical formula. In a sense, one is reversing the work done by the cracking, since that is a process that changes the chemical formula, however, when one puts the molecules back together, one changes them structurally. Basically, one is making isomers.
However, I do wonder if reformation also includes the saturation of hydrocarbons; as in, making alkenes and alkynes into alkanes. This obviously requires cracking, since double and triple bonds must be broken down into single bonds. If this is a part of reformation, that would mean the term applies to a wider process than just making isomers, since an alkane cannot be an isomer of an alkene/alkyne.
Perhaps isomerization is the creation of isomers, but within any field of chemistry, whereas reforming applies specifically to petrochemistry?