Schematic Explanation
That is the power section of a high power switching regulator, of a type called buck-boost.  The input voltage can be above, equal to, or below the output voltage.  Linear Technology (now a part of analog Devices) has a line of control chips for this.  Here is one, and the datasheet has a good applications section.

https://www.analog.com/media/en/technical-documentation/data-sheets/ltc3779.pdf