add definitions for pool, node, and scaleset (#17)

* add defs for pool, node, and scaleset

docs/terminology.md

@@ -59,4 +59,33 @@ An
 Each fuzzing task has a set of required and potentially optional containers that
 are used in a specific context.
 
-[More info on Containers](containers.md)
+[More info on Containers](containers.md)
+
+## Pool
+
+A pool is a group of nodes to run [Tasks](#task).  Pools enable users to
+specify which group of [nodes](#node) their task should run on.
+
+Pools are defined by:
+* `name`: the Name of the pool
+* `os`: The operating system of the node (`linux` or `windows`)
+3. `arch`: The CPU architecture of the nodes (only `x86_64` for now)
+4. `managed`: Is the pool made up of OneFuzz managed [scalsets](#scaleset)
+
+## Scaleset
+
+A scaleset is an [Azure Virtual Machine
+Scaleset](https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/overview),
+of which the entire lifecycle is managed by OneFuzz.  All of the VMs in the
+scaleset are automatically setup to connect to the OneFuzz instance as a
+[Node](#node).
+
+Scalesets can run on almost any [Azure VM
+Image](https://docs.microsoft.com/en-us/azure/virtual-machines/linux/cli-ps-findimage)
+(use the URN for the image) or [user-provided OS images](custom-images.md).
+
+## Node
+
+A single compute host to run tasks.  Right now, these are only VMs in a
+[scaleset](#scaleset), though support for on-prem or third-party cloud-hosted
+nodes will be available in the future.