Let’s start with the simplest use case. Blockchains manage blocks, and in the blocks, they could have different things. But one of the most popular use is: the block payload is a list of transactions, that transfer a crypto currency, a value between accounts.
Then, what is the simplest use case for connecting two blockchains based in transactions? That the transfer in one blockchain should be reflected in the other blockchain:
Why this transfer is special? Because the first transfer has an special target account: every value transfer to that special account will be reproduced as a transfer in the second blockchain. The transfer value is the same: if you transfer 1000 units in the first transaction, then you will transfer 1000 units using the second (automated generated) transaction.
You controls the first account (Acc1) in the first blockchain. Knowing that account, the second blockchain will transfer the second transaction using an associated second account (Acc1’) in the second blockchain. Then, you can use that value in the second blockchain, having access to Acc1’.
The amount transferred in the first transaction will be locked in the special account of the first blockchain. In another use case, we will describe the recovery of that value, to be released again.
The special accounts are managed by the connection system, not by human beings.
More use case are coming, stay tuned!