aussehen = sehen + aus, and in this case aus plays like 'like'. If you check the dictionary, aussehen means 'appear'(to someone), 'look like'. Sehen itself means 'see'. There are many 'Trennbare Verben (split verbs, verb which contains preposition in front of verb) in German. For example, ansehen means look at something. Ich sehe ihn an. means I look at him. Hope it helps.