Could anyone ELI5 what weight is?
If you are referring to weight as in "Not enought weight" with POSII (Proof Of Stake) then it's the age of the coin you have in your wallet.
In short, it's how old the coins you currently having in your wallet in form of confirms.
With enough age (weight) of the coins, you start to produces POS blocks with in term means by holding you coins in the wallet, you get an small amount of coins just for holding coins in your wallet, open and running.
So in short weight means with weight you produces a small amount of coins via Proof Of Stake (POS) depending on coin age.
Examble of block #1559828 which is POS block -
https://chainz.cryptoid.info/xmg/block.dws?1559828.htmThe wallet contain an amount of 447.0266122 XMG with enough weight to generate 0.01237373 XMG
Hope this is good enough explanation