This is the user who frequently checks news, sports updates or connects to social media. The seemingly casual person who browses through things of interest, but without taking much action.
This user gets away from stress at work or fights boredom by switching on the mobile to browse, play, watch or listen. This user has fleeting attention and is difficult to engage.
This user is looking for important information that he needs rights now. Perhaps location based information or decision-making information. He's the guy who might take action on a relevant ad or offering.
This does not mean to say that marketers have to ignore the first two, but it tells us to get our priorities right - who to engage first and with what.