Task Manager - please explain

[PC Hobbyist]

Can someone please explain to me what the different values under "physical memory", "kernel memory" and "system" all really mean? I don't mean just what they point to, but maybe a little explanation of what they are.

For example, in the physical memory (which I take to mean RAM), it says I have 1534 total, but then it says cached=784 and free=347. So where did the rest go?

 

[PC Hobbyist]

For example, these two windows give me information that appears to be contradictory.

Look at the yellow sections I highlighted. One says I have almost no RAM left (only 1 free) while the Resource Monitor says I am only using 41% of my RAM (which matches the bottom status bar of the Task Manager).