A Frag Grenade is an throwable explosive used by pilots in Titanfall and Titanfall 2. The basic explosive device known to all modern soldiers, the Frag Grenade is still an incredibly useful weapon. In this game, it is not as popular as the Arc Grenade, but is arguably better in building interiors, long-range throwing, and is second to none at killing pilots. It does not create the visual distortion that the Arc Grenade does, but has a much larger blast radius and is much more lethal in a much wider area.
Frag Grenade is an explosive ordnance in the game. It has a 2.5 second fuse, it will start beeping after being held for 2.0 seconds, where it's too late to throw it. Frag Grenades are extremely effective against Minions and are capable of destroying an entire squad with one grenade. Against Pilots, Frags deal a considerable amount of damage in close range and can kill a Pilot in full health. Frag Grenades do not deal considerable damage against Titans, but can be used as distractions.
Frag grenades are powerful and only one is required to kill a Pilot in full health. They can bounce off walls, making them ideal for clearing out hardpoints in Hardpoint Domination or flushing out enemies behind cover. They are also a great distraction strategy against Titans and other Pilots.
Contrary to popular belief, Frag Grenades do not kill using the force from the explosion (that is what Satchel Charges do). "Frag" stands for Fragmentation. The grenade explodes, flinging pieces of metal composed of the grenade's casing in all directions. It is these flying steel pieces that kill those in the blast radius.
Needless to say, for simplicity, the game shows just an explosion. If the fragments were included in the animation, GPU load would be increased, it would be difficult to see the fragments anyways due to the speed they fly (as fast as bullets, but without tracers, and smaller than most bullets).