In League of Legends there are 131 champions and each one of them is different.

First of all, the champions are divided into different arch-types:
•Tank
•Support
•Marksman
•Mage
•Assassin
•Fighter (Bruiser).

Each arch-type has a totally different role in the game and to have a good team composition you need a good mix of those. The champions have stats. Stats can be upgraded by buying items or with in-game champion buffs. There is a vast variety of stats:

•Health Points: Your championcan start with 350 (squishy) to 500 (tank) HP at level 1. And they gain +70 HP each level (squishy) to +110 HP each level (tank).

•Mana: Starts from 150 to 300 mana at level one and +30 mana per level to +60 mana per level.

•Attack Damage: The damage your champion deals with his auto-attacks without any items is called base AD. Every champion is able to auto-attack. AD goes from 40 AD (non-ad champions) to 58 AD (fighters and marksman) at level 1. And you can get + 2.5AD per level to +4.2 AD per level.

•Ability Power: This stat is mostly used by AP mages/casters but you start with 0 AP at the start of the game and have to work your way up to an infinite cap in the game much like Attack Damage with in-game items and champion buffs but AP only affects QWER abilities and sometimes champions passives.

•Attack Speed: Attack Speed is a number that tells you how many attacks per second you can do. Attack speed is different from the other stats. Every champion has base attack speed that never changes during the game. It can only be upgraded by items which give attack speed.

•Armor: Goes from 10 to 20 at level 1. It is mostly built by tanky bruisers which are looking to be un-killable monsters in the late game.

•Magic Resist: Every single champion starts with 30 magic resist at level 1. It is mostly built by tanky bruisers which are looking to be un-killable monsters in the late game.

•Range: This is the auto-attack range. Melee champions have 125-175 range. Ranged champion’s attack range goes from 425-650 but it is possible to buff it with certain buffs that champions have.

•Movement Speed: Each champion starts with movement speed that goes from 325 to 355 but it doesn’t grow over time.
The only way to buff it it’s with items and in-game champion buffs.

Those are the basic stats that the most skilled players must be relying on. Of course there are other stats like critical chance or lifesteal but it depends very much on your type of playstyle and it’s something that people who elo boost per example don’t like relying on, because it is not controlled by the user.Elo boosters utilize a mix of these stats