Frequency Capping: It is a term in advertising that means restricting (capping) the number of times (frequency) a specific visitor to a website is shown a particular advertisement. This restriction is applied to all websites that serve ads from the same advertising network.
What does the last line means here? I am not able to understand. And whats "Same Advertising Network"
It means the same advertising provider. The people who actually do the bids on the advertising space.
Examples would be Atlas, Doubleclick, Rocket Fuel, Quantcast, etc, etc.