Farming involves supplying liquidity to XTZ/tzBTC pair with a twist: you can use additional leverage thanks to the funds provided by Lenders.
Farming screen shows how much APY one can earn from supplying liquidity in xtz and tzBTC assuming max leverage (i.e. 4x).
You can see how much liquidity is provided by farms in total from the field "Total Value Locked" while "Total Loan" denotes the amount of borrowed funds. Both figures are shown in USD and the corresponding currency.
While the page for Farming is conceptually similar to Lending one, it has a distinction between fields "Contribution" and "You can Invest". The first one denotes how much of your own assets you plan to contribute to the Farm, while the second one demonstrates the final total investment size. It depends on how much leverage in addition to contributed funds you plan to employ. Leverage is adjusted by the slider below.
Finally, "Collateral ratio" chart shows what percentage of the total loan collateral ratio (your investment marked at market prices) constitutes. The larger this figure is the safer is Farming and further you are from getting liquidated (at the cost of having lower returns due to less leverage employed).