Q:

What is the meaning of "scope" in a Smart Contract?

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.

A:

EOSIO organizes data in the fashion described in the graphic below.

The scope usually refers to the account in relation to which the data is stored. So eosio.token stores each account's token balance in an accounts table. But instead of a single huge accounts table, each user's account is kept in a small table scoped to that user.
Shout out to the EverythingEOS developer courses for going over this stuff.

