In the extra section of Genki 1, Chapter 10, the book introduces 〜方面 "serving... areas" in the context of trains and stations. However, it does not go over how to use it, and I can't find anything online about its usage and difference from say 〜行き which is also taught.
How is it used in the context of trains?
方面 has a similar meaning to 方角, but 方面 is more vague and abstract. For example, 大阪の方角 refers to that specific direction (yellow), whereas saying 大阪の方面 conveys an image of a broader spread (red).
The translation "serving ... areas" may be used specifically when 方面 is used on train information panels. Saying 大阪方面 vaguely indicates areas toward Osaka, hence the translation.
However, I think ～方面 is most commonly used to indicate the direction of a loop line, such as Yamanote Line, where the final destination of the train cannot be defined.
(source)
大阪行き simply indicates the train's final destination is Osaka Station.
In daily usage, 電車は大阪に向かった means the train's destination is Osaka, but 電車は大阪の方面に向かった means the train went in the direction of Osaka, i.e., it is not certain if it actually reaches Osaka. But you don't have to worry about this when you see 大阪方面 in a signboard.
Grammatically, 方面 is a noun or a noun-forming suffix. You can use it like 大阪方面への電車, 富士山方面の景色, 九州方面から来ました and so on.
