Add error definitions

docs/modules/ROOT/pages/explanations/decisions/comp-function-error-handling.adoc

@@ -15,6 +15,13 @@ This document will discuss in detail the problem we face with composition functi
 * A comprehensive guide on how we should deal with error management.
 * A solution to missing managed resources from desired function when errors occur.
 
+== Definitions
+
+* Fatal Result error - the error that stops crossplane from reconciliation which means the desired object will not be applied in the cluster.
+Typically safe move which will ensure no changes to the service but we rarely use this type of error.
+* Warning Result error - the error that we mostly return and one that endangers the service.
+Crossplane will still apply the desired state with a warning error therefore returning early in CFs may result in managed resources being deleted.
+
 == Proposals
 
 Proposal 1:: Manage Errors in CFs