我们 [wǒmen] and 咱们 [zánmen] both means: we, but when I should use 咱们， 我们？
What is the difference?
我们 can be used both formally and colloquially across all Chinese speaking regions, while
咱们 appears more in spoken language and more in Northern China.
我们 may or may not include the listener, depending on the context, while
咱们 almost always includes the listener.
咱们 includes both parties, there can be a strong or even exclusive focus on one party, either the speaker (e.g.
瞧咱们的 = "we'll show you how it's done") or the listener (e.g.
咱们不怕 = "let us not be afraid"). This type of usage is very common in Northern China but can be quite unfamiliar/unnatural to other Chinese speaking regions.
咱=我：咱不懂他的话。 咱们=我们 including the listener: 同志，您别客气，咱们军民是一家人。 As possessive pronoun: 咱=咱们（的）：咱村全都富起来了。（Here it could be a villager talking to another villager, or talking to an outsider, or even an outsider talking to a villager (the outsider was trying to sound friendly and close by using the term to include himself as part of “us”. The outsider could simply say 你们村全都富起来了。but he would sound alienating himself from the villagers or the listener.