間 is a word which a native Japanese speaker uses or hears almost every day. Usually it just means "time", "interval", "space", "room", etc. For example:
- 締め切りまで間がある。 There is some more time left till the deadline.
- 間もなく東京です。 Arriving at Tokyo Station soon (lit. "in no time")
- 行と行の間をあける to leave spaces between lines, to double-space
Unsurprisingly, such a basic word has dozens of idiomatic expressions which might make little sense if you translated it too literally:
- 間が悪い (lit. "time is bad") to be done at the wrong time
- 間に合う (lit. "match the time") to make something on time
- 間男 (lit. "in-between man") paramour, secret (male) lover
But these may not be of particular interest to native English speakers who don't want to learn Japanese.
So 間 is not really a cool or special word to native Japanese speakers. I'm sometimes surprised to see mundane Japanese words are introduced to foreign countries as something mysterious and cool. For example, see: What is the exact meaning of "kaizen"?
That said, I am vaguely aware that some people have found the concept of 間 as unique to Japan. I found this long article in English: MA: Place, Space, Void. The article also explains how 間 is important in certain fields of Japanese art. Honestly speaking, I'm not totally convinced that 間 is such a difficult word, but I think the linked article covers almost everything that you might need.