Played a bit of Dota 2 but I couldn't get into it, overall I just found it boring.

i avoid mobas regardless

That's not what pay to win means. Of course it's possible to play LoL and never pay any money, but the things you can spend money on allows you to accumulate items that give you a performance enge in games faster than people who choose to play for free and grind for those items. Whereas a non-pay to win game is a game where there are no in-game buffing items you can purchase with real money.

I've never played any MOBA games. Can you tell me exactly what makes a MOBA game?

Never felt like people who spent money has an edge on me. Sure they can buy high ranked accounts, but they are still bad. Sure they can buy 20 rune pages, but they are still bad. Sure they can buy all the champions, but you only need to be good with one.

And btw the in-game buffing items is bought by currency only achieved by playing the game. You can level up to 10 and spend $10,000 but you won't have any advantage over someone who spent $0.

Usually a 5 per side match, on a map with 3 lanes that are defended by allied and enemy towers and the lanes converge at a home base at either end of the map. In between lanes is open areas noremally referred to as jungles where there are other things you can kill to gain in game money, XP and sometimes temporary buffs. In each lane you have squads of minions that spawn every 20-30 seconds that you kill (the enemy minions) for in game money and XP (or some variant that lets you gain levels and obtain buffing items). The object of the game it to destroy enemy towers in the lanes and then push into the enemy base to take the final objective which may be a home tower or a base "guardian". Most matchess take between 20 - 60 minutes depending how evenly matched the teams are.

Some games have variants that include more of a battle arena with no lanes and different objective for winning (like accumulating points from killing enemies) and other variants involve a one lane map and 3v3 or 1v1 match.

Well that's kind of irrelevant. Player skill is not what determines whether a game is pay to win.

Pay to win is where you can buy items with real money that makes a character better than the character without those items. LoL has that with runes. If 2 players are evenly matched with a character and one has runes and the other does not then the one with runes will win in a mirror match. If you can buy the runes with real money then that's pay to win. in LoL you can buy the runes with real money, hence LoL is pay to win.

See  bold.

You can't buy runes with real money...

Don't like them, don't care for them.

My understanding is that you can, albeit indirectly, so not in the way I described above. You can buy IP boosters which gives you more IP from playing, which can then be used to buy Runes. Is that not true? Also you can pay money to buy champs, which frees up IP to buy runes. 

It seems like there's the potential to infinitely argue about whether LoL is pay to win in any meaningful way. I guess it's wrong to say it's strongly pay to win, but it has pay to win elements. But the matter is simple with a game like Smite because there are no equivalents to Runes in Smite so there can never be any argument about pay to win.