OK I will.

With a firearm (and I will use a modern day firearm as an example) you insert the cartrage INTO the chamber, cock the weapon and squeeze the trigger. This causes the firing pin to puncture the primer and thus ignite the powder INSIDE the casing. This sudden pressure buildup causes the bullet to become separated from the casing while the barrel allows to bullet to travel one way and that is out of the weapon and to it's target.

With a crossbow, you pull back the string by use of either your arms or a crank and by doing that you load the LIMBS with energy. once the string has been pulled back you put a bolt/arrow ON the STRING and squeeze the trigger causing the locking mechanism to dissengage from the STRING. The energy in the LIMBS propels the bolt/arrow by use of the STRING to send the arrow/bolt to it's target.

With a compound bow you first put an arrow on the STRING then pull the string back with your arm by use of a hand held trigger mechanism and by doing that you load the LIMBS with energy. Once the string has been pulled back you squeeze the trigger causing the locking mechanism to dissengage from the STRING. The energy in the LIMBS propels the arrow by use of the STRING to send the arrow to it's target.

And your point is???