I always get the concepts “critical path” and “critical section” confused.

The “critical section” is the part in your algorithm which you must hold a lock for; whereas the “critical path” is an idea from hardware design which relates to the time taken for the longest combinatorial logic that needs to be processed during a clock cycle, thus limiting the frequency you can run your clock at.

Although the terminology “critical path” came from hardware, the same terminology is used in software. ChatGPT has a fairly good write-up on the two uses of the term “critical path”.

I learned a little more about this in Introduction to VHDL for FPGA and ASIC design.