URL encoding converts characters into a format that can be safely transmitted over the internet. 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 characters values in the ISO-8859-1 character-set. URLs cannot contain spaces. URL encoding normally replaces a space with a + sign.