Can someone clarify this whole GSM vs CDMA thing?

so info i've found on gsm vs cdma concerns verizon , at&t in states. i'm in canada, have bell, rogers, fido, telus.

out of curiosity, of companies carry cdma iphone 4 , carry gsm? cdma have sim card slot or not iphone 4?

, have iphone 4s bell. gsm or cdma?

thanks.

 

http://en.wikipedia.org/wiki/list_of_canadian_mobile_phone_companies

 

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