In constructing a confidence interval estimate of a population mean or testing a hypothesis about a population

Question:

In constructing a confidence interval estimate of a population mean or testing a hypothesis about a population mean, why is the t used so much more often than the normal Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...