I would like to give you some encouragement. If you are looking for a definition of a word like "module" then you are probably learning about programming as a skill just as much as you are learning B4J as a language. If that is the case then don't confuse learning B4J with learning programming - these are two connected activities that will progress in parallel. Yes, you will find much more documentation about learning Java (say) than about learning B4J. On the other hand you will also need a tool (an "IDE") to write and edit your code - that is somethiong that B4J provides also. Try looking at Eclipse, a very popular IDE, and you will soon discover why B4J is such a good tool.
I have been writing software, on and off, for several decades, but I have never done anything much with internet software. Whenever I try to gat to grips with some documentation I very soon come across a word, such as "socket", and I am immediately stuck. I know what a socket is in the real world, but not what it means in reference to the internet world. You are going to face this all the time if you are new to coding whichever approach you take - do not be put off.
@DonManfred has pointed you to some good sources but be prepared for some hard work at first until you find your way around - that is going to happen whatever path you take. And do not underestimate the assistance that you will get from this forum, which I believe is unbeaten by any other coding package. Basic questions will get high quality replies just like any others. Keep going.