Since I have read the tutorial. I don't understanding the following:
Note that scopes are used to logically separate tables within a multi-index (see the eosio.token contract multi-index for an example, which scopes the table on the token owner). Scopes were originally intended to separate table state in order to allow for parallel computation on the individual sub-tables. However, currently inter-blockchain communication has been prioritized over parallelism. Because of this, scopes are currently only used to logically separate the tables as in the case of eosio.token.
To my knowledge, scopes are only used by eosio.token. And not yet within multi-indexes.