Can someone explain to me how this works, if you want to borrow 100 ETH how is that secured? Or is the loan unsecured?
Of course it is secured, all lending platforms work in similar way - lets simply say you have to secure 100 ETH loan with 200 ETH deposit, that's it.
EthLend difference from Salt or other platform is that it is more open/free - you can secure your loan with different cryptocurrencies, not just BTC or ETH or LEND.
There's a short article about Lending platforms on BitcoinMagazine:
https://bitcoinmagazine.com/articles/options-borrowing-and-lending-cryptocurrency-are-rise/To summarize, this lending area is new in crypto world and has a lot of potential - all players can be winners including EthLend, Salt, etc.