In the Bitshares official website they're explaining the functionality of the tool and in general look like Ethereum.
What makes Ethereum different of Bitshares?
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Vitalik has made the analogy that Ethereum is to Bitshares as CPU is to ASIC. See the 54 minute mark of this Silicon Valley Ethereum Talk from early 2014.
Daniel Larimer generally agrees in this bitsharestalk comment but he feels Bitshares is more like a GPU in comparison.
Basically, Ethereum can do a wide variety of things (Turing-complete) whereas Bitshares is geared towards specialising in decentralised e-commerce.
The Ethereum Whitepaper describes Ethereum as follows:
Ethereum intends to provide is a blockchain with a built-in fully fledged Turing-complete programming language that can be used to create "contracts"
The original Bitshares Whitepaper states:
Within the BitShares network, we have created a new type of financial product called a Polymorphic Digital Asset [PDA] that can track the value of gold, silver, dollars, or other currencies while paying dividends to holders and avoiding all counterparty risk. BitShares extends Bitcoin technology to provide many features of traditional currency, checking, savings, and brokerage instruments
The Bitshares 2.0 Whitepaper states that Bitshares is a decentralised exchange that "supports trade not only in digital assets, but also traditional financial instruments and securities on the blockchain."