的话，from a pure grammatical point of view is used for marking the end of your assumption and normally follows by a decision/result/statement based on your assumption.

...的话 = if...

的话，is a word kinda like "yet","zilla".... it doesnt have any meanings at all if you just looking into these two words simply. most of the time its use of assuming tone. for example, if you like it,i'll buy it for you.(如果你喜欢的话，我买给你)。this is one of the most common useage of this words. it's kinda like the "yet" word's function in the sentence "have you already done that yet?" otherwise, it's just a usage habbit, mostly using in the answers, and means nothing at all. for example, What kind of sports do you like most? Well, for sports, I prefer basketball. (你最喜欢什么运动？呃，运动的话，我最喜欢篮球)

的话=if you are talking about .... 如果没有时间的话=if you are talking about "If you don't have time" you can say 如果没有时间. However adding 的话 will soften your tone, and sounds nicer to your counter party. Also we often use this pattern ×××××+的话，here 话=××××××， it is just a language habit that emphasize ×××××（the topic). A：你喜欢看什么电影？ B：电影的话，我喜欢文艺片。

This word is used just to point out that the sentence in front of "的话" is a premise,and the sentence after "的话" is something that would happen under that premise. It's ok to leave out "的话", but I suggest not. The use of "的话" is more common in oral Chinese.