They work somewhat similar, in the sense you gain extra processing power.
Turbo is a temporary boost however.
It will work on 1,2, or 4 cores depending on certain conditions.
Mainly when under a heavy workload, if thermal conditions etc are all OK.
Once the workload is complete, it falls back to default specifications.
Turbo can not be adjusted. only turned on or off.
Where as when you OC, you can adjust the performance (or speeds) however you wish to.
Also, you will always have that performance gain you set, even if the CPU is only under a partial load.
Overclocking can be dangerous if done improperly as well.
Some more info about how Turbo works if you're interested:
Processors — Intel® Turbo Boost Technology frequently asked questions
Intel Turbo Boost - Wikipedia, the free encyclopedia
