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Let's say you could run all thof the FAANG companies on one smart contract platform and still have space for more stuff. EOS ERC-20 token allows you to claim a piece of that amazing upcoming platform when it's out in mid 2018. The token doesn't worth anything. You can use the token to claim a piece of EOS when it's out. Think of it like the old bank notes when they were actually backed by Gold.

Essentially it's a base platform for developers to use to create Dapps but with much better performance than ETH. The token itself COULD be used to buy or sell things, but vimukthi explains that in his reply. Technically, ANY crypto, or really anything could be used to barter and trade with.