\typeout{msg}
Prints msg on the terminal and in the log file. Commands in msg that
are defined with \newcommand or \renewcommand are replaced by their
definitions before being printed.
LaTeX's usual rules for treating multiple spaces as a single space and ignoring spaces after a command name apply to msg. A \space command in msg causes a single space to be printed.
\typein[cmd]{msg}
Prints msg on the terminal and causes LaTeX to stop and wait for you
to type a line of input, ending with return. If the cmd argument is
missing, the typed input is processed as if it had been included in
the input file in place of the \typein command. If the cmd argument
is present, it must be a command name. This command name is then
defined or redefined to be the typed input.