No - but I can explain some terms further. ELI5 isn't a *literal* requirement here - 5 year olds don't generally have the language yet to understand thermodynamics.

That said - thermal energy is just a fancy name for heat - and thermals is me making up a unit of measure for the amount of heat.

You have to measure heat differently from temperature. Temperature tells you how hot a substance is but different substances hold different levels of heat. (Strictly speaking the correct term is Joules but I called them Thermals because I was making up numbers and didn't want to make you think my numbers were anywhere close to correct).

The measurement of heat capacity is actually based on joules of energy per kilogram per degree Kelvin but in simpler terms it means if you have a pound of water and a pound of air (yes, air has weight) both can be the same temp but the water will hold more than 4 times the amount of actual heat energy than the air. What happens when the amount of heat hits its limit? The temperature goes up.

Looking at it another way - if you have a pound of air and a pound of water - but the water is at 0F and the air is at 10F - if you moved ALL the heat from the air into the water, the water would only go up to just under 2.5F, not 10F - because water can absorb so much more heat than air. Same amount of energy but in different materials - so less temperature change in the denser material.

Now in reality temperature won't move 100% from one to the other - instead they'll reach a balance where the temperatures equalize - which will still work out to about 2 deg F for both the air and the water since the water will absorb most but not all the heat.

If that doesn't clarify please lmk what you need help with, happy to keep trying to come up with examples. :)