Most blockchains work in sequential fashion.

A block can contain many transactions, so it "appears" as if it is doing a lot of things at once.

..the problem is, when the block gets full, you have to WAIT until the next block can take transactions.

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With EOS, it is multi-threaded, and can support sidechains. This means that multiple chains (like a multi-lane highway) can exist.

So there isn't just 1 block that gets full and you have to wait.

There's many blocks that can simultaneously take transactions and exit "off" the highway, and merge back on it again. Which stops waiting, and traffic jams.

It's pretty complex and detailed. These are just the overall simplistic descriptions I've created to try and paint a picture of the difference.