First it's best to know the difference between power weapons and the kinetic/energy weapons. Power weapons include: swords, rocket launchers, grenade launchers, sniper rifles, fusion rifles, linear fusion rifles, and shotguns. With the exception of one exotic grenade launcher being an energy weapon (Fighting Lion) these are always power weapons.
Now the difference between energy and kinetic. These weapons include: auto rifles, pulse rifles, scout rifles, hand-cannons, side-arms, and submachineguns. These weapons cannot be interchanged, meaning that even though there are mods that can change the element of a weapon (on both energy weapons and power weapons) they cannot be changed to kinetic and vise-versa.
You can quickly tell the difference between a kinetic and energy weapon in 2 ways. Energy weapons will obviously have an element, this will be shown with the purple, red, or blue icon of the respecting element type. Another more subtle way is the direction of the weapon in the icon. Kinetic weapons will always face from the grip in bottom right to the barrel in the top left, while energy (and power) weapons will face from bottom left to top right.
Sunshot is an energy handcannon and its icon faces from left to right.
Strum is a kinetic handcannon and faces right to left.