Learn English – Use of ‘since’ and ‘ever since’

The two terms are closely related, and even interchangeable in many cases. However, the two words focus on different things. Alliance is more about mutual interests or benefit, while coalition is more about doing some action.

The use of both terms is not limited to the political context. They can be used in other contexts: military, financial, commercial, technological, and so on. Having said that, I agree that coalition is used most often in the political context for "a temporary alliance of political parties forming a government or of states" (see below).

Here are their definitions, according to Oxford dictionary:

alliance (noun)
1. A union or association formed for mutual benefit, especially between countries or organizations.
1.1 A relationship based on similarity of interests, nature, or qualities.
1.2 A state of being joined or associated.

coalition (noun) A temporary alliance for combined action, especially of political parties forming a government.

Here is a quote from Get Them On Your Side by Samuel B. Bacharach (chapter 5):

Formally defined, a coalition is a politically mobilized collection of interest groups or individuals committed to achieving a common outcome (i.e., resistance or change). Through political mobilization you create a group that has some sense of shared goals and/or a sense of connected interests. A coalition is an alliance for joint action.

In short, a coalition is an alliance for joint action.

Don't be so hard on yourself. English is very difficult.

This talks about present perfect tense - which have been by itself falls under, and have been by itself can be used to describe an experience:

You can use the Present Perfect to describe your experience. It is like saying, "I have the experience of..." You can also use this tense to say that you have never had a certain experience. The Present Perfect is NOT used to describe a specific event.

Have been + {-ing form of verb} is present perfect continuous tense, which is different. That's used to talk about something that has started at some time in the past and is still ongoing or happening now.

Putting would in front of either of these now says that the action or experience did not happen because of something. Typically a clause will precede or follow explaining why, typically starting with but.

I would have been to Japan, but I was unable to afford the trip.

I hated her guts. I would have otherwise gone to the skating rink.

I would have been going with him, but he sort of creeped me out. So I went with her instead.

We would have ruled the entire kingdom, yet their relentless attacks on our land proved it impossible.