SigningAuth or Certificate Authority

What are signing/certificate authorities ? They are organisations that key a copy of your public key and your name so that you can verify who owns the key.  What are the pros and cons? well the benefit is nobody can impersonate you if they get into your web account for instance and say that they are you and give out public keys that they only have the private key information.
In other words like a man in the middle attack they can't impersonate you easily. The bad side is that groups like NSA can easily identify who is sending a message once they have a copy of your public key. Some signing authorities issue free certificates which make it easy for people to write web pages to use SSL. Lets encrypt says that they will be issuing free, automated and open certs in September 2015.