Question about cross shard transaction

Web3 Protocol
1

Hi, I have a questions about cross shard transaction at Harmony mainnet:
Assume I have 100 ONE on shard 0 and shard 1, and I want to send 200 ONE to my friend Ben, who has an account in shard 3. Then how will the transaction work?
Thanks!

2

hi Jackson, you would do two transactions:

  1. transfer from your address to friend address with from-shard 0, to-shard 3, and amount 100
  2. transfer from your address to fiend address with from-shard 1, to-shard 3, and amount 100.
    note that there is a small gas fee for each of these two transactions.
3

What is sharding? I never understood it.