We will give a very elementary introduction as to how the notion of vertex operator algebra arises as the algebra of correlation functions governed by genus-zero, Riemann surfaces with tubes, along with a sewing operation, following the work of Yi-Zhi Huang. In Conformal Field Theory, these Riemann surfaces with tubes model propagating strings which collide to form new particle states. We will also put this interpretation into the context of the theory of operads.
Links:
[1] https://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] https://www.mpim-bonn.mpg.de/de/node/3444
[3] https://www.mpim-bonn.mpg.de/de/node/249