What is process sleeping state on macOS?

Question

I'm just in the process of sending my photo library (60GB) to iCloud and I noticed that the cloudd process, which is responsible for the transfer, sometimes has the status of sleeping and the transfer still takes place. What does sleeping mean in this case? I check the process status with top program in the Terminal application.

Screenshot from Terminal

Answer 1

Taking a look at the man page for ps(1)

I       Marks a process that is idle (sleeping for longer than about 20 seconds).
R       Marks a runnable process.
S       Marks a process that is sleeping for less than about 20 seconds.
T       Marks a stopped process.
U       Marks a process in uninterruptible wait.
Z       Marks a dead process (a ``zombie'').

At any given time there is at most one running process per core in the CPU. Process that can be scheduled on the core but are not currently running are called "sleeping", they also may be waiting on the completion of some IO, in this case the cloudd process is probably either waiting for the network hardware to send some data to iCloud, or waiting on the disk to read some data.