Basic attacks are the default attack in Paragon. The attack scales with level and is either melee or ranged. Some heroes have special basics, like Revenant, who has an ammo count instead of infinite bullets, or abilities that boost basics and get boosted by basics, like Khaimera's Unleash and Spirit Regeneration. Basics can also land critical strikes, doing 50% bonus damage.
Basic attacks are countered by basic armor, which reduces the amount of damage done. Armor scales with levels and can be built with cards, reducing the amount by 1% of health for every unit of armor. Armor penetration is subtracted from armor. If the total is above the armor value, it is ignored (the enemy will have zero armor.