Clearly you didn't read that intro I linked to.
Your first question was an entirely acceptable request for direction; your second question was solved by googling the words "command line". Apparently, you start by googling the question?
Two different questions, one total failure to try.
Hackers love questions by non-techies, but attitude counts for a lot.
Instantaneous no-effort information feeds directly into your comprehension (bypassing the brain, eyes and fingers) do not exist; any request for such a thing is not appreciated. If a question can be answered by the first page of google search results, it can be assumed due diligence was not performed.
Question: what is the command line?
Answer: did you google "command line"?
Response: I am very upset at you for making me google something -- it took me three link clicks to find the answer. That's way too much effort, so you are a jerk for making me do it.