Verb Stem + 고: "and"
This is a Final Verb Ending. It means "and". You can chain as many as you want together.
Note that the endings applied to the last verb apply to all verbs in the "and". "생각하고 봤다" means "I thought and saw". Note how the past tense G + ㅆ다 applies to both 생각하다 and 보다.