Definition - What does Synthetic Cork mean?
A synthetic cork is an optional wine bottle stopper made out of various plastic compounds. These "corks" are not biodegradable, but they are recyclable.
The introduction of synthetic corks was initially an answer to cork shortages, and initially, it was believed they had advantages as they protect bottled wine in many ways natural cork could not; such as from oxygenation, leaks, etc.
WineFrog explains Synthetic Cork
Initially, synthetic cork was seen as a better alternative to natural cork wine stoppers. They were believed to lower the risk of TCA and corked wine. However, as time went on, it was proved that while there are less instances of TCA with synthetic corks, it still happens.
It has also been proved that eighteen months after bottling, synthetic corks allow for harmful amounts of air to enter the bottle. This is unlike natural cork, where air is allowed to pass through in very small amounts as long as the wine is stored on its side and in conditions with proper humidity and temperature ranges.
The original argument for synthetic cork that it solved the cork shortage problem has also been debunked. There is no cork shortage.
Small disadvantages of synthetic cork, though it may give the very satisfactory "pop" sound, is that they are often difficult to remove and you cannot replace it back in the bottle