I don't know about site meter in particular but the difference between visits and page views is generally this.
visits - number of people touring through your site. think of it like a department store. each visit is how many people walk through the front door.
page views - number of different pages on your site that are viewed. in the department store example, it would be the number of departments walked into total regardless of the number of people. this number should be higher because hopefully each visitor would view multiple pages.
visit time could = 0 if the person doesn't fully load the page or site meter doesn't accurately record the leave time. this is software specific and i don't know anything about site meter.