Sure and sorry for the late reply. Ethereum has only one main blockchain. It's like how bitcoin has its own blockchain that consists of a string of "blocks" or digital ledgers. (Those digital ledgers keep track of all transactions.) However, as you may know, Bitcoin's blockchain is congested and that poses a problem for tracking all transactions and thus creates the problem of long transaction times. Ethereum only has one main chain and so all the transactions have to go through that one chain. Sidechains for Stratis may be considered backwards compatible meaning that it isn't like a hard fork. Projects may create dedicated side chains using the Stratis platform and thus work on that specific chain. The side chain would be connected with the main chain, but wouldn't bloat the main chain.