A blow job is basically when a guy's like, "Hey! Wanna suck my dick?" and then a very generous and possibly drunk girl is all like, "Okay." After the initial agreement the guy drops his pants and the girl starts sucking his huge horny boner until and eruption/explosion of cum blinds the girl for life.
After receiving permission from his girlfriend, Johnny the man-whore got his cocked sucked good and hard; it was his grandma's first blowjob.