URLs can only be sent over the Internet using the ASCII character-set.
Since URLs often contains characters outside the ASCII set, the URL has to be converted. URL encoding converts the URL into a valid ASCII format.
URL encoding replaces unsafe ASCII characters with "%" followed by two hexadecimal digits corresponding to the character values in the ISO-8859-1 character-set.
URLs cannot contain spaces. URL encoding normally replaces a space with a + sign.