What does the COLLATE keyword do when creating a sqlite index?

According to the sqlite3 documentation,

The COLLATE clause following each column name defines a collating sequence used for text entries in that column. The default collating sequence is the collating sequence defined for that column in the CREATE TABLE statement. Or if no collating sequence is otherwise defined, the built-in BINARY collating sequence is used.

What does a collating sequence do, and what is a BINARY collating sequence?

From stackoverflow

• It is the way that the sql engine orders data internally. Binary Collation does what it suggests, it does a binary comparison. Generally its the fastest collation though i have never quantified it, As it checks bit patterns it is case and accent sensitive.