A conventional loan is a mortgage that is not guaranteed or insured by any goverment agency, including the Federal Housing Administration (FHA), the Farmers Home Administration (FMHA) and the Department of Veterans Affairs (VA). It is typically fixed in its terms and rate.
A fixed interest rate loan is a loan where the interest rate doesn't fluctuare during the fixed rate period of the loan. This allows the borrower to accurately predict their future payments. Variable rate loans, by contrast are anchored to the prevailing discount rate.
ARM (Adjustable Rate Mortgage):
A variable-rate mortgage, adjustable-rate mortgage (ARM), or tracker mortgage is a mortgage loan with the interest rate on the note periodically adjusted based on an index which reflects the cost to the lender of borrowing on the credit markets.