BTUs explained? (Simply)

I'm 18 years old and going into my fourth week of college for HVAC. So far we have talked about states, matter, the components of refrigeration, OHSA etc. I am understanding all of that slowly, I still have some trouble with it but I'm slowly absorbing it.

However, when my professors talk about BTUs, I am at a loss. I understand that it is a way to calculate heat and that it stands for British Thermal Units but that's all I can understand. When I try to read my textbook about it, I get confused because it goes so in depth.

Can someone please help me? - NostalgicDuck

The simplest explanation is the definition. It's the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. - Zackhood

So if I had a pound of water sitting at 70° F, if the temperature was raised to 75° F that would be 5 BTUs? - NostalgicDuck

I think he got it. By jove he got it! - toomuchpork