If you have an adversarial mindset (which is absolutely healthy) and want to understand it well enough to not immediately come up with counterarguments whose only valid reply is "RTFM", yes, it takes at least 20 minutes. But regardless, I'll bite.
DAI has a couple of intended use-cases. I will focus here on the "stable coin" asset, meaning you should be able to expect it's value to not go up or down over time. It is inherently debt.
The main component of DAI is "CDPs", Collateralized Debt Positions. There is a smart contract on the ETH blockchain. Smart contracts are computer code on the blockchain that are "open trustless execution", meaning you can inspect the source code, verify that it matches the deployed bytecode, and be certain that any transaction follows the rules. In DAI, there is no entity that can even theoretically exit-scam you.
The configuration parameters of this smart contract is set by votes by the holders of the MKR token. This token is traded on public markets and is the speculative token of the ecosystem.
You can deposit assets into this smart contract. The current version of DAI only takes ETH, but the intention is that MKR holders will consider any significant asset representable on the ETH blockchain. This includes other stablecoins (think fiat-backed tokens), tokenized equity or government bonds (which have already been issued on the ETH blockchain), tokens backed by commodities like gold, etc.
When you deposit assets into the smart contract, you get DAI in return, representing a loan backed by the deposited assets. How much DAI you get in return is determined by an oracle (meaning a smart contract providing data external to the blockchain). This oracle is aggregated from several other oracles, similarly public and approved by the MKR governance. In general, the system is over-collateralized at any point in time.
There is an incentive and liquidation system around the whole things that goes a bit further to ensure that the price remains stable despite fluctuations - and so far the DAI/USD price has remained really close to 1 throughout the ETH/USD long bleed of 2018, including short periods of high volatility.
There is some degree of risk involved of course, most notably including the oracle price feeds. There is a road map to both increase transparency and decrease the possibility of collusion between oracle providers.
There is also the "emergency shutdown", which involves freezing and instant liquidation, but this comes at a big cost to the MKR holders who have to approve it.
Despite having been running for several years and having dozens of people (I think over 100 now?) it is, of course, still to a large part an experiment that is still evolving. But so far it has been performing better than I thought. And there is no way you could call it a scam.