"^" means "raised to the power" in mathematics, so
10^5 means 10 raised to the 5th power, or 10*10*10*10*10
'e' in mathematics represents the constant 2.718 (approx) which occurs a lot in nature. It is called Euler's constant.
So, e^5 = e raised to the 5th power, or 2.718*2.718*2.718*2.718*2.718
-273.15 = negative (or minus) 273.15. This is minus 273 and 15/hundredths. If it were -273.90, you would say it was minus 273 and 9/tenths (or 90 hundredths).