If you'd like to delve deeper into the world of FPGAs and Lucid, check out "Learning FPGAs: Digital Design for Beginners with Mojo and Lucid HDL" by Justin Rajewski. It's available on Amazon and is a great resource for understanding and ultimately designing your own FPGAs.
An FPGA allows you to design digital circuits. Digital circuits are basically just a bunch of logic gates (and, or, nor, etc.) connected together to perform a specific task. The designs that you create can range from something as simple as a counter that blinks an LED to something as complex as a multicore processor.
The flexible architecture of FPGAs has shown great potential in sparse networks, which is one of the hot trends in current machine learning applications.Another important feature of FPGAs, and one that makes them even more flexible, is the any-to-any I/O connection.
The SoC FPGA integrates a hard processor and a programmable logic, such as those from ARM (Advanced RISC Machine). Now to answer your question, the best way to learn design FPGA is to pursue the VLSI SoC Design Online Course from Maven Silicon, one of the top VLSI Training Service Providers for both Online and Offline courses.