title. i kinda want to watch the esport scene
you get gold from giving the last hit in opponents and minions. basically, you farm to get gold while trying to kill your opponents, getting stronger and creating a snowball. you have to destroy the towers in order to get the lanes moving in your favor, thus having control of jungle, doing objectives (dragon/baron/destroying enemy's jungle) and having more firepower to finish the match by breaking the enemy's nexus. but it's not that linear and a lot of big teamfights might happen
you cannot understand that much without playing, but if you have the aforementioned things in your mind, you'll know what's going on in general