Arnis, also known as kali or eskrima/escrima, is the national martial art of the Philippines. The three are roughly interchangeable umbrella terms for the traditional martial arts of the Philippines ("Filipino Martial Arts", or FMA), which emphasize weapon-based fighting with sticks, knives, bladed weapons, and various improvised weapons, as well as "open hand" techniques without weapons.
Many Filipino systems focus on defending against and/or reacting to angles of attack rather than particular strikes. The theory behind this is that virtually all types of hand-to-hand attacks (barehanded or with a weapon) hit or reach a combatant via these angles of attack and the reasoning is that it is more efficient to learn to defend against different angles of attack rather than learn to defend against particular styles, particular techniques or particular weapons. For instance, the technique for defending against an attack angle that comes overhead from the right is very similar whether the attacker uses bare fists, a knife, a sword or a spear.