1. The attacked party is always going to call the enemy terrorists, no matter what their actions are, since if they'd call them freedom fighters, they'd acknowledge their cause.

2. Freedom Fighters target an enemy occupying force, with the intention of being a large enough pain in the ass to drive the occupant away.
Terrorists either target the enemy population at home to apply political pressure, or they target whoever's available - even fellow countrymen - just to spread terror and chaos. (Whatever they hope to achieve with it)

So to me the difference is their choice and location of targets. Freedom Fighters fight at home and they fight/attack/ambush/blow up military targets.
The rest is terrorism.