What are the differences in credit scores?

What is FICO score? Is it a score all by itself or does each credit bureau have a FICO score? I ve read that credit Karma is not completely accurate as far as score goes, just good for seeing what s on the credit report. But what about going directly to Experian or Transunion or Equifax? Is that accurate? When applying for a credit card or mortgage what score do they use and Where would I get a score that compares that that one?

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