That's one definition - it's a more technical one.
But fire is the heat that fuels life. However, it can kill and destroy. If you don't respect fire, it can literally consume you. Without fire, though, life as we know it cannot exist. If the heat of the sun and stars did not exist, everything would be frozen over, and atomic reactions would come to a permanent halt.
Blah blah blah.
Time to mold fire chakra!
Stand in the middle of the field, and begin to mold regular chakra. Don't focus on anything other than the heat of the sun.