Match making

Can someone please explain to me how the match making works, cause i cant understand how 3 plat V players , 1 gold III and 1 gold II players can play against 1 plat III, 1 gold I , 1 gold II, 1 gold V, and 1 silver I. And on an other note , do you know the difference between a silver and a plat jungler ? I really don't get this match making. For people who have started to climb from low divisions and done it in a short time(few days) they know what the difference in skill between a single one is . Most of my latest games have been gifted to the enemy team. And i feel like when you get to point where you go to you proper skill rank it is really up to [ luck (matchmaking { RIOT })] to climb higher. What i don't get is i had 10+ W over L, and after a few gifted games i am matched with someone in silver 1 with 7 LP. my rank is Gold I. Why is the matchmaking base on latest win or lose rate and not based on rank? Why is it in my promo to plat i have to play with players with a much higher rank than that? Why is it that gold I player is matched with a silver I player with 7 LP? 5 division difference! And i really hope that Riot employ gives me a proper answer!

Thank you