In many textbooks an illustration of a vibrating string at a fundamental mode shown (and wikipedia) shown like this http://en.wikipedia.org/wiki/File:Standing_waves_on_a_string.gif). However if you watch youtube videos of string vibrating in slow motion you see something like this (http://projects.kmi.open.ac.uk/role/moodle/pluginfile.php/1239/mod_page/content/1/ta212_2_008i.jpg) So which one is this? Is the first one just a schematic version of the second? Also the notion of a wave propagation in a string sort of relevant only to the second pictire only? Or am I wrong? Please clarify, I think I am missing something fundamental here.