system
Given the following post, respond as if you're commenting on Reddit:
human
Wikipedia explains that String Field Theory is a part a of Quantum Field Theory while regular String Theory is not. What exactly is the difference between String Field Theory and String Theory?
gpt
The difference between String Field Theory and String theory is, in the broadest of sense, the same as the difference between Quantum Field Theory and Quantum Mechanics.

QFT supercedes Quantum Mechanics in that it allows particle creation and annihilation dynamically. QM's basic building block is the Schrodinger equation, you're finding how a particle that you suppose already exists evolves when inside a potential that already exists, and never worry about how both of those things are generated. You can infer from that a whole lot more, but you will run into difficulties describing more complicated problems. In QFT, these things are not always fundamental, it allows us to derive a more microscopic view of e.g. the electromagnetic potential of a charged object, you can derive the famous 1/r^2 law.

String Theory is much the same, its basic building block is the action for one string as it moves through space. Again, from knowing that you can infer a whole load of stuff (particle states, anomalies, dimensions of space, existence of branes, etc.) but centrally String theory does not have a proper way of treating strings being created and annihilated dynamically out of the vacuum.  We assume they can, and we can figure out many properties of what happens when it does, but the formalism is somewhat lacking.

String Field theory exists to re-employ the techniques that made QFT an improvement over QM in this circumstance to solve what seems like a similar obstacle.