This episode explains significant figures, which are the meaningful digits in a number that reflect a measurement's precision. It outlines rules for identifying them: non-zero digits are always significant; leading zeros are never significant; and trailing zeros are significant only if there's a decimal point. It notes that scientific notation is the best way to avoid ambiguity. The rules for calculations are different for addition/subtraction (limited by decimal places) versus multiplication/division (limited by significant figures). The episode stresses that significant figures are a crucial tool for honest scientific communication.