In most role-playing games, the archer character usually gets a bad wrap for hitting like a mosquito biting a woolly mammoth. They may have range, but a lot of games have them shooting paper darts instead of the missiles of death that they're supposed to fling at enemies. But in Path of Exile, the Ranger has some fairly deadly potential, and this build is a good way to exemplify that as it looks and plays spectacular. This level of destruction is usually attributed to spellcasters with area-of-effect spells, but this Ranger build looks like it can give pure magic a run for its money.
This build promises 30 thousand critical damage down the line, which is quite enticing. It is described as fast, safe, and can kill packs very quickly -- something you would want to use for runs. As it says on the name, you primarily use Tornado Shot to take out mobs after cursing them with Split Arrow. The indicated main weapon for this build has a 100% pierce property to it, so you will be cursing and damaging plenty of enemies with ease. There are plenty of Tornado Shot builds out there, but this particular one is great for beginners and casual players due to its low-budget requirement for Path of Exile items while still being powerful enough to be viable.
Leveling this build up does take you a bit of a detour since the active skills needed are not that good early in the game. You would want to use Poison Arrow or Firetrap to level Split Arrow in your weapon swap, then get Lesser Multiple Projectiles from the Weaver quest to get the second piece of the puzzle. Once you get Tornado Shot, you can start running through mobs and speed up the process while crafting a physical bow every 10-15 levels until you arrive at level 53 when you can finally equip Infractern.
The reason why Infractern is used for this build is that it has the unique property of "Arrows Always Pierce", which means that you can consistently kill mobs of enemies stacked one after another. Combined with Tornado Shot, it makes for a devastating combination that is already pretty good on its own, but you then combine other support gems and skills to it for greater effectiveness. It does also say "Cannot Leech" though, which is why it is cheap since people are scared off by that drawback and works to your advantage.
Set your sights at a good 5-link Infractern and put Tornado Shot + Lesser Multiple Projectiles + Added Fire + Physical Projectile Attack Damage + Increased Critical Damage to complete your main weapon. What you then have is a weapon that can curse and kill mobs at a distance with impunity, and you can then use hit and run tactics to hit as many as you can while keeping yourself from getting hit. This build is easy to pull off and very rewarding for those who go all the way with it.