This is a flexible way to work with FM synthesis without a lot of re-patching. The first row is the synth part, the second is just sequencing for convenience while auditioning sounds.
Each oscillator is routed to an input on the matrix. The corresponding output is sent back to the oscillator’s FM input. The last two outputs go to the audio out. So, each oscillator can modulate itself or any other oscillator to the degree set by the knob. It can also be mixed into the audio output directly.
Anyone familiar with the FL Studio Sytrus synth will be familiar with this setup.