(content removed on scope grounds)
The scope of THIS forum is the Seamly2D patternmaking software and pattern construction using that software. Unfortunately, we do not have enough volunteer time to answer basic questions about terminology that far outside the scope of this forum.
I can suggest that you put the following words into a search engine “discussion forum basic sewing pattern making”. I just did that search and found a large number of forums that might be open to discussing your questions.