You may use this SSL lookup tool to verify if SSL Certificate on any server has been installed correctly, and can be trusted with valid dates.

An SSL (Secure Sockets Layer) certificate is a digital certificate that is used to establish a secure encrypted connection between a web server and a web browser. It ensures that all data transmitted between the web server and the browser remains private and secure.

SSL certificates are issued by Certificate Authorities (CA), which are trusted third-party organizations that verify the identity of the website owner and issue a certificate. When a web browser establishes a connection to a web server that has an SSL certificate, it will check the certificate against its list of trusted CAs to verify that it is valid and that the website is authentic.

Once a secure connection is established, the web browser and web server will negotiate an encryption method to use for the session. All data transmitted during the session will be encrypted, making it much more difficult for anyone to intercept or eavesdrop on the communication.

Having an SSL certificate is important for the security of any website that handles sensitive information, such as passwords, credit card numbers, and personal information. Most web browsers display a padlock icon in the address bar when a website has a valid SSL certificate, which gives users an indication that the website is secure and trustworthy.

SSL certificates can be purchased from a variety of Certificate Authorities (CAs), which are trusted organizations that issue digital certificates to verify the identity of websites and their owners. Some of the most popular CAs that sell SSL certificates include:

1. GlobalSign
2. DigiCert
3. Comodo
4. Sectigo (formerly Comodo CA)
5. GeoTrust
6. Thawte
7. RapidSSL

You can purchase SSL certificates directly from these CAs, or through resellers that offer a variety of SSL certificates from multiple CAs. When purchasing an SSL certificate, it's important to consider factors such as the level of encryption offered, the reputation of the CA, and the cost.

Keep in mind that you will need to follow the CA's process for verifying your domain ownership and the authenticity of your website, as well as install the certificate on your web server, in order to start using it. Some CAs also offer support and tools to help you with the process.

TLS (Transport Layer Security) and SSL (Secure Sockets Layer) are protocols that are used to secure communication over the internet. They both provide encryption and authentication to ensure that sensitive data is transmitted securely between two devices.

The key difference between TLS and SSL is that TLS is the successor to SSL, and is considered a more secure version of the protocol. SSL was originally developed in the 1990s, and has since been replaced by TLS as the standard for secure communication on the internet.

TLS and SSL both use certificates to establish trust between the communicating parties and to verify the identity of the server. They both also use encryption algorithms to encrypt data transmitted over the internet, making it unreadable to anyone who intercepts it.

However, TLS provides stronger encryption algorithms and more secure certificate authentication than SSL, making it less susceptible to hacking and other security threats. TLS also provides better error handling and allows for future upgrades to encryption algorithms, making it a more future-proof solution for securing internet communications.

For these reasons, most websites now use TLS instead of SSL to secure their connections. The vast majority of web browsers now display a padlock icon and "https" in the address bar to indicate a secure connection with a website that uses TLS.