Width-sensitive (_WS) collation takes into account the number of bytes used to represent a character.
When using width-sensitive (_WS) collation, if a character can be represented both as a single-byte and double-byte character, they will be sorted separately in the query results.
On the other hand, with width-insensitive collation, SQL Server will consider both the single-byte and double-byte representations of the same character as identical.
For example, width-insensitive collation treats E=mc² and E=mc2 as equal. On the other hand, width-sensitive collation treats them as different.