Single, double, triple, quadruple, etc. refers to the number of times a trick occurs
Dual means a trick is done with both feet/skates at the same time. For example doing a front foot toe flip and a back foot toe flip at the same time is called a dual toe flip.
Moving towards your body's center.
Moving away from your body's center.
Left foot is leading. Right foot is the back foot.
Right foot is leading. Left foot is the back foot.
The opposite of your normal stance. For a skater who rides Regular, switch means right foot leading. For a skater who rides Goofy, switch means left foot leading.
There are several variations. The default is when your back foot crosses frontside of your front foot.
This is a term in skateboarding for when you're riding switch but your body is oriented away from your direction of motion. Since freeskates are more symmetrical, the term fakie doesn't have the same meaning. You may hear people use Fakie as an alternative to Switch.
The direction that your belly button points in. When referring to a spin, such as "a frontside 180", frontside means the belly button is pointing towards the outside of the circle of rotation. When referring to a throw trick, frontside means the skate spends most of the duration of the trick on the frontside.
The direction that your back points in. When referring to a spin, such as "a backside 180", backside means the belly button is pointing towards the inside of the circle of rotation. When referring to a throw trick, backside means the skate spends most of the duration of the trick on the backside.
The part your feet come into contact with.
On top of the deck. Provides traction.
This is where the wheel connects. Depending on the model, some skates have connected decks and trucks.
On some models of freeskates, the truck either has a built in or attached plate used for performing grinds.
Some models of freeskates have a cushion between the deck and trucks to provide for a smoother ride and softer landings.