Some questions about keyword research.

1. Why we must do keyword research?

Because, if you dont do your research first, how would you knwo if a keyword is worth wasting time and money on to rank for? If not many people use that keyword to search, why would you want to rank for that keyword.




2. There are 3 match type : Broad, Exact, Phrase. What does each mean?

Broad match
It means you want the results to contain the keywords in any order.


Example:
If I search for "making money online", I would get this:

Making money online

online money making

an online money making method




Exact match
Means you want the results to contain the exact keyword.

example:
If I search for "make money online", I would get only this:

make money online



Phrase Match
It means you want results with all the keywords in the search terms in the same order.

example:
If I search for make money online, I would get this:

I make money online
Ways to make money online
I need to make money online





3. I have watched some videos guide when doing keyword research, the only show ideas closely related to my search terms is checks, others videos ignored it. I want to know what is the difference? which one is better(on or off)?

I am sorry, but I didn't understand this question.



4. After generating the result, i see that some keywords are choosen, some are ignored. I want to know which criteria we based that we choose and ignore the others.

Keywords are chosen based on many different factors depending on the niche and keyword itself. Usually, the chosen keywords are the ones that have high volume monthly searches, but have not many people are competing for them. Thats the basic of it, but of course, as I mentioned depending on the niche, different numbers could mean different things.