I'm watching Lord of the rings (which I know is supper accurate) and how the orc arrows shoot through the Gondorian armor like its nothing. Does a real life set of armor stop arrows well or do they cut through pretty easily?
Stopping arrows is one of the main jobs of armour. For penetration of plate armour, the key quantity is the energy of the arrow. A good source for info on penetration of armour (by bullets and other weapons as well as arrows) is Alan Williams, The Knight and the Blast Furnace, Brill, 2003. Some quantitative information was quoted from this by /u/Marclee1703 in https://www.reddit.com/r/AskHistorians/comments/1l1t9w/in_the_medieval_era_could_arrows_pierce_plate/ in response to an earlier asking of this question. To summarise here,
To defeat mail: an arrow needs 120J of energy
To defeat plate: an arrow needs over 200J of energy.
A high draw weight longbow can deliver over 100J, possibly up to 150J, at point-blank range, which suggests that knights who wore an extra layer of armour (e.g., a felt gambeson, as used in the Crusades; Saladin's biographer, Ibn Shaddād, wrote that the Franks wore "very heavy felt and so stout a coat of mail that our arrows did no harm ... I saw foot soldiers with as many as ten arrows in their backs, who marched on just as usual without breaking rank" (quoted in many sources, including Williams) over their mail would have been safer.
However, note that much of the armour on a late Medieval plate armour is thin enough so that it can be penetrated by crossbows or arrows. Usually, the breastplate and helmet are thick enough so that they can be considered arrow-proof (often 2-3mm thick), but arm and leg armour is usually thinner (often 1-1.2mm, or even thinner), and can be penetrated. Arms and legs aren't particularly vulnerable, since the armour is strongly curved, and a crossbow bolt or arrow is unlikely to hit square-on, but it is quite possible for an arrow/bolt to penetrate.
So it wouldn't be like orcs shooting through Gondorian armour like it isn't there, but arrows bouncing off plate or being stuck in textile-mail-textile sandwiches, with the occasional lucky hits through arm and leg armour (and in gaps in the armour, like backs of legs, the occasional lifted visor, etc.).
For more discussion of armour vs arrows, see https://www.reddit.com/r/AskHistorians/comments/7mu6z2/in_bernard_cornwells_agincourt_a_character/ with responses by, among others: /u/Hergrim /u/MI13 /u/WARitter