Catalan - A little different Spanish or a whole other story?

Is Catalan really different from Spanish? Do I need to know basics of Catalan when I go to Barcelona? Will people in Barcelona understand if I speak Spanish? Is Barcelona good place to learn Spanish?
Many tourists that are planning to come to Barcelona are asking themselves these questions. That is why we will present here interesting facts about Catalan language as well as useful language tips a tourist will need while traveling to Barcelona. There first thing You need to know is that Catalan is a different, autonomic language mostly not similar to Spanish at all.