cd $HOME/Desktop/foo var world/images
Where "$HOME/Desktop/foo" is one argument, "var" is another argument, and "world/images" is another argument. The blank space has an special meaning for the shell, it's a separator. You can bypass that by quoting the string, so bash will understand it as a single argument.
You could also quote the relevant part, if you are 100% sure that the rest of the string will never contain spaces:
, yes, you could do that, but in this case the string is not known beforehand. Just quoting is more convenient, unless you are willing to process the string after reading it to substitute spaces and other special characters.