Hello David
Let’s take a step back and see what all the commands that start with collect actually do. The collect command is used to specify additional fields to be recorded for each network traffic flow. These fields are called nonkey fields.
Key fields are used to define and identify a unique flow (like source/destination IP addresses, ports, protocol types). Nonkey fields provide supplementary information about each flow. They enrich the flow record but do not define the flow itself. So additional information about the specific flow is collected, but only as nonkey fields.
For example, the collect ipv4 destination prefix command you mentioned is used to gather statistics about destination IP address prefixes in the packets being monitored, as nonkey fields. The complete command syntax is:
collect ipv4 destination {address | {mask | prefix} [minimum-mask mask]}
Take a look at this Cisco command line reference documentation for more information on the specific command. The same document includes all of the collect commands as well.
I hope this has been helpful!
Laz