Mnemonics

"backslash", "escape", "hack"

• used to "back out" of a syntax to a character's original meaning
• used to "hack" around, or "escape", special characters

When used inside a regular expression

\ in front of any character will change it from a metacharacter to a literal, or visa versa.

When used in a Signature

\ before a sigilless name is a parcel binding.
\ before a sigilled parameter prevents parcel collapse.

Operators containing this character

Modifying a reduction operator such as [\+] (modification of [+]) creates a lazy feed of intermediary results..

Other Uses

unary \ as a noun in front of an argument or arguments creates a Capture
\ in front of whitespace creates an unspace which is used to jam spaces in where they don't belong.
\o \c \x and \d used inside an interpolated string introduce literal characters