Usually a miner buys high percentage of the project
Traditionally Junior sells and a major buys in to a project for X percentage of the mine. The proceeds are used to fund the mine, much like CR.
INR + Sibanye Stillwater buys half of ioneer's Nevada lithium project in $490 million - INR is still listed
Rio Tinto reaches agreement with Turquoise Hill Resources (Note TRQ:TSX is a mid size miner and even they sell a share of the resource to fund a mine if it is too big)
In the Case of AVZ and FFX it is little different as the investment is coming from non miner, so to become a miner the expertise will be hired/contracted.
There is blurred distinction between Explorer and Junior.
Many Exploration companies specialise and become pure explorers. But it depends on sectors ie Copper, Tin, Oil and Gas there are many specialized Exploration companies. Where as for Gold and Lithium most try to become a Junior.
Juniors have found a resources and they are seeking to become a miner.