Thunder is a physical shockwave. As it travels, it interacts with different layers of air temperature. Sometimes, the sound waves are refracted (bent) upward into the higher atmosphere. This creates a "shadow zone" on the ground where the lightning is visible, but the sound literally passes over your head. Why Do We Call It "Heat Lightning"?
Generally, thunder is rarely heard more than 10 to 15 miles away from the strike. What Causes Lightning Without Thunder
Here is a blog post breaking down the science behind this glowing phenomenon. Thunder is a physical shockwave
In reality, there is no such thing as silent lightning. Here is the science behind why you’re seeing the flash but missing the roar. Distance is the Deciding Factor This creates a "shadow zone" on the ground
While "heat lightning" isn't a threat to your immediate area, it is a reminder that a real thunderstorm is nearby.