rato is an indefinite amount of time, short or long, so it can be used as "moment", "ago", "while", "(some) time", etc. E.g.:
"en un rato" ---> "in a moment"
"hace rato" ----> " a while ago" or "sometime ago"
"por un rato" ---> "for a while"
"bastante rato" ---> " quite some time"
continuaré jugando wii "un rato más" ---> J'll play wii "just another moment" (and then...five hours later)l...."bueno, un rato más"......