There are two main economic theories that explain interest rate determination: the loanable funds theory and the liquidity preference theory. The loanable funds theory states that interest rates are determined by the supply and demand of loanable funds in the credit market. The liquidity preference theory argues that interest rates are determined by individuals' preferences to hold money balances rather than invest or spend. There are also various theories about the term structure of interest rates and how they vary based on maturity and risk.