A puncture can generally be repaired if it occurs on the central portion of the tyre. If a puncture occurs outside this area, near to the tyre's sidewall, it cannot generally be repaired. This is because the sidewall carries the largest load when you drive and the repair process typically used to fix punctures can weaken the sidewall's structure. The sidewall also needs to be able to flex adequately and any patches applied in this area would be far more likely to come away from the tyre.
Runflat tyres, however, cannot be repaired. Runflat tyres are designed to be able to be driven on for a short period even after a puncture, meaning they allow you to get home or to a garage.