The adverb 함께 means together; and like 같이 it can follow noun-plus-과/와, noun-plus-(이)랑 or noun- plus-하고 to mean together with [so-and-so] or simply with [so-and-so]. The noun in these expressions usually denotes a person or other living being. The word 함께 is used in exactly the same way as 같이. [Also see Section 6.4.]
아버님과 같이 or
아버님하고 같이 or
아버님이랑 같이 or (together) with Father
아버님과 함께 or
아버님하고 함께 or
아버님이랑 함께
친구와 같이 or
친구하고 같이 or
친구랑 같이 or (together) with my friend
친구와 함께 or
친구하고 함께 or
친구랑 함께
같이 갔어요 or They went together.
함께 갔어요