Describe CPU and Memory resources.

docs/user-guide/compute-resources.md

@@ -40,6 +40,32 @@ about pod resource requests/limits.  A *pod resource request/limit* for a partic
 type is the sum of the resource requests/limits of that type for each container in the pod, with
 unset values treated as zero (or equal to default values in some cluster configurations).
 
+### Meaning of CPU
+Limits and requests for `cpu` are measured in cpus.  
+One cpu, in Kubernetes, is equivalent to:
+
+- 1 AWS vCPU
+- 1 GCP Core
+- 1 Azure vCore
+- 1 *Hyperthread* on a bare-metal Intel processor with Hyperthreading
+
+Fractional requests are allowed.  A container with `spec.container[].resources.requests.cpu` of `0.5` will
+be guaranteed half as much CPU as one that asks for `1`.  The expression `0.1` is equivalent to the expression
+`100m`, which can be read as "one hundred millicpu" (some may say "one hundred millicores", and this is understood
+to mean the same thing when talking about Kubernetes).  A request with a decimal point, like `0.1` is converted to
+`100m` by the API, and precision finer than `1m` is not allowed.  For this reason, the form `100m` may be preferred.
+
+CPU is always requested as an absolute quantity, never as a relative quantity; 0.1 is the same amount of cpu on a single
+core, dual core, or 48 core machine.
+
+# Meaning of Memory
+
+Limits and requests for `memory` are measured in bytes.
+Memory can be expressed a plain integer or as fixed-point integers with one of these SI suffixes (E, P, T, G, M, K)
+or their power-of-two equivalents (Ei, Pi, Ti, Gi, Mi, Ki). For example, the following represent roughly the same value:
+`128974848`, `129e6`, `129M` , `123Mi`.
+
+### Example
 The following pod has two containers.  Each has a request of 0.25 core of cpu and 64MiB
 (2<sup>20</sup> bytes) of memory and a limit of 0.5 core of cpu and 128MiB of memory. The pod can
 be said to have a request of 0.5 core and 128 MiB of memory and a limit of 1 core and 256MiB of