Why are their two point systems FSW (100) and Express Entry (600)

Im actually very confused by the FSW and why its points system is different from Express entry…

https://www.canada.ca/en/immigration-refugees-citizenship/services/immigrate-canada/express-entry/become-candidate/eligibility/federal-skilled-workers/six-selection-factors-federal-skilled-workers.html

Per this page, If i am an intra-company transferee and I have a job offer to start working in canada, do i then qualify to apply through FSW rather than the regular express entry system. Additionally, does this mean (though not clearly specified on that link) that I can apply PR through federal skilled worker point scale /100 only if Im already in canada working for my employer on a temporary work visa ?

FSW is one of the three progs under Express Entry. FSW itself has a different scoring system (100 Points) where one needs to score over 67 points to be considered for the FSW prog. If one can cross this point threshold then his application goes into the EE pool and is then compared with others based on the CRS score. All EE applications are judged in the common pool using the CRS scoring system (600+ points).

If you have a job (Arranged employment) then you get 10 points in the FSW score and up to 200 in CRS (CRS – D. Additional points)

Does arranged employment include intra company transfer? There is no concrete details on this on the website (kind of unnecessarily critic). And who or what decides whether i apply as FSW or regular Express entry?

There is no official thing called inter company transfer. It’s just you leaving one company and joining another since the Canadian registered company is a separate entity by itself regardless of ownership. Yes so you have arranged employment and would be deserving those points.

FSW is 1 of 3 progs that fall under the common Express Entry umbrella (pool) the other two are FTP and Canadian Experience class. If you can get those 67+ points then you qualify to enter the EE pool as an FSW candidate. from there on you will then be selected to complete the EE process based on your CRS points