I don't understand the Treeline meta

What about is difficult to understand? Maybe I can help shed some light on it.

You have a mage bot lane, a bruiser top (sometimes an ADC), and then a Jungle. Alternatively, you run a Mage bot with an ADC (with smite) and a Support in-lane and attempt to force the bruiser out and constantly invade the enemy Jungle.

Champions that take advantage of short maps, choke points, really strong laning phases, or a lot of easy solo gold shine through a ton. Champions like Darius, Cho, Illaoi, Taric, Kayle, Poppy, Lucian, Orianna, and Anivia are some examples of strong TT characters.

Everyone in this thread so far from skimming looks very wrong

https://rankedboost.com/3v3-tier-list-lol/

This is from master/challenger TT players

Meta is from what I understand Mage bot with a jungle and a support. The support helps the jungle clear and pushes top in with the jungle sometimes and they'll gank around bot. Better description in the website

What summoners are taken in the support + carry lane I know one of them is supposed to run smite but it doesn't make much sense to me for them to take it instead of the support