The origin on why ' ' is used as a space in URLs

Question

I am interested in knowing why \'%20\' is used as a space in URLs, particularly why %20 was used and why we even need it in the first place.

Answer 1

It uses percent encoding. You can see the Percent Encoding part of the RFC for Uniform Resource Identifier (URI): Generic Syntax

A percent-encoding mechanism is used to represent a data octet in a component when that octet's corresponding character is outside the
allowed set or is being used as a delimiter of, or within, the
component. A percent-encoded octet is encoded as a character
triplet, consisting of the percent character "%" followed by the two
hexadecimal digits representing that octet's numeric value. For
example, "%20" is the percent-encoding for the binary octet
"00100000" (ABNF: %x20), which in US-ASCII corresponds to the space
character (SP).