The Trap Jaw "Gun"...
The Little Lightning Rod thing, could attract ions or protons to power up the cannon. (Similar to how the Mega Buster from Megaman charges up)
The vents are just that... Vents. Added later on after problems with overheating. Problem with that many vents; they let in dust and other stuff that jams the cannon and forces TJ to use his other attachments.
The "Scope" is a Blue Laser guiding system. Trap Jaw rarely uses it since it makes his blasts weaker. ( The Guidance system HAS to draw energy from somewhere.)