Question

describe string theory?

Answer 1

The string theory describes that every atomic/subatomic particle is some energy as a quantum vibration in their respective energy field.

Answer 2

The starting point for string theory is the idea that the point-like particles of particle physics can also be modelled as one-dimensional objects called strings. 
String theory describes how strings propagate through space and interact with each other.

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hope this helped you
@chris