It's a good thing you asked this question, as the difference between Attacks and Special Attacks is very important in Pokémon.
In Gen III and earlier, all Water, Grass, Fire, Ice, Electric, Psychic, Dragon, and Dark-type attacks were Special, while the others were Physical. (stolen from DarthDestiny's answer)
Okay, so the thing about Pokémon is that in addition to having Attack and Defense stats, Pokémon also have Special Attack and Special Defense stats. This is very important, as Pokémon have different base stats for each. For instance, you could be wondering how a Pikachu's Thunderbolt does practically nothing to a Chansey, but if it uses Quick Attack, Chansey easily gets KO'ed. The reason behind it: look at Chansey's different defensive stats. 250 HP and 105 base Special Defense make special attacks such as Thunderbolt useless, but Quick Attack is physical, so the damage it does is based off of Chansey's Defense (base 5). Sorry for going off-topic.
So to answer your question, Special Attack differs from Physical Attack for 2 main reasons: first, a Pokémon usually has different Attack and Special Attack stats, and thus will do more damage with either one or the other. Second, the amount of damage done is determined by either the opponent's Defense or Special Defense.
Typhlosion's Special Attack is 109, by the way. Its other stats are here.
