I would like to point out that I am writing this with people who have no tabletop experience in mind, so if I seem like I'm only going over really basic things, please don't hate me or my game.
With that out of the way, let's look at the most basic and recurring mechanic of the game: Actions! Actions are your primary way of interacting with the world. For any narrative to exist within a game, you must do something. Fortunately in TotA we have made it easy to do things. Almost every single action is some type of Skill Check. What this means is, if you want your character to try and do something that accomplishes an outcome, you roll the dice. You compare your result to a number set by your task to determine whether nor not you succeed. Because different characters are good or bad at different things, every character has a set of skill values. When making a Skill Check, you add the appropriate skill value to the roll to increase your chances of success by that percentage. If you have no value in a given skill, you may still attempt that action, but you get no bonus to your roll.
Tales of the Arcanimus has many different skills. Want to sneak past an enemy patrol or pick a bystander's pocket? Roll Stealth! Want to set a broken bone or pick a fallen comrade up off the ground? Roll Medical! Want to navigate through a storm or swing across a yawning chasm? Roll Adventuring! Even attacks are Skill Checks; the three types of attacks are Melee, Marksmanship, and Sorcery. Each of these is a skill.
Whenever you attack someone, you make a roll. But so do they. Unlike an unopposed action, whose difficulty is a static value, defenders oppose attacks with their own rolls. Attacking is a contest between one side's skill and the other's armor (with a healthy degree of random chance thrown in on both sides!) If the attacker's total roll is higher, the attack hits, damage is dealt, and any effects are inflicted. If the defender totals higher, then the attack is avoided. Simple as that!
Naturally, damage is something you want to avoid. In TotA, every character has 10 Hearts; no more, and no less. Combat in this game is designed to be fast paced, unlike other games of the genre in which tanks are set up to sponge and heal damage in lengthy battles of attrition. Therefore, most attacks are scaled to do between 3 and 6 damage on average.
Of course, this doesn't mean that if you're attacked you don't have options! As a defender you can select choices that allow you various bonuses, for instance shielding some of the incoming damage when attacks hit you, or getting in extra hits when they miss, and more!