Hello,
I assume you're referring to the terms in this document:
http://www.cisco.com/en/US/products/ps6120/prod_models_comparison.html
Concurrent Threat Mitigation Throughput is the rough network throughput (i.e. Mb or Gb per second) that you can achieve when using both firewall services (NAT, application inspection, etc.) and Intrusion Detection/Prevention services (i.e. threat scanning, attack alerts).
With the 5505 platform, these are the speeds you can achieve using both the firewall and the AIP-SSC module. Likewise with the 5510-5540 firewalls and the AIP-SSM. For the 5585 platforms, this is the combination of a firewall and IPS SSP module.
Hope that helps.
-Mike
