A Starter Introduction to LLMs

Is there a beginner’s guide to LLMs?

I am guessing I need to set up aider + an LLM like Deepseek 2 on
local hardware.
And I understand that I need a certain kind of processor (Ryzen 5),
a GPU 1.2 larger than the LLM, (20GB?)
and 32GB of DDR5.

But a good overview of all this would be very helpful.
Are there smaller LLMs catering to specific niches or
individual programming languages for instance?