Okay kiddo, so imagine you are sitting on a swing and you start to move back and forth. Each time you move, you create waves in the air around you. These waves are called photons.
Now, sometimes your swing doesn't move very fast and the waves (photons) you create are very gentle and slow. These are like soft photons. Other times, when you swing really fast, the waves (photons) you create are stronger and faster. These are like hard photons.
Soft photons are just like the gentle waves you create on the swing when it's moving slowly. They don't have a lot of energy and they don't travel very far. However, they can still be very important in some scientific experiments, like when studying atoms and particles.
So, the next time you're swinging and creating waves, remember that some of them are like soft photons, gentle and not very powerful, but still very interesting to scientists!