What is the difference between set affinity and lock thread?

[NikasZalias]

Hello, I wanna understand what is the difference between both of these features? From what I tried to test it looks like both features does the same job. Although, I can see the difference in C code, but still looks like that the achieved goal is the same.

FEATURE 2 - PIN A THREAD TO A CPU (set affinity) FEATURE 3 - LOCK A THREAD TO A CPU/CORE