What is an SSL certificate?
An SSL certificate makes the site available over HTTPS.
What it is
An SSL certificate, usually TLS today, proves that the browser is talking to the server that belongs to this name. It encrypts the connection. Without a certificate the site stays on HTTP, or the browser shows a warning before anyone even sees the content.
The browser checks the name in the certificate against the name in the address bar. The two have to match.
What it is made of
The certificate names the name it is valid for, and a date until which it is valid. example.com and www.example.com are two names. A certificate for only one of them makes the other warn. Wildcards such as *.example.com cover the subdomains, not the bare domain, depending on how it was issued.
What goes wrong
Certificates expire. An expired certificate is not a small notice, the site is practically closed for visitors. Renewing means getting a new one in time and giving it to the server without breaking the connection. By hand on every server, that is a task someone forgets, usually on a Friday.
What you otherwise look after yourself
The certificate hangs on the name, so on DNS. If the name points somewhere else, the certificate on the right server does not help.
How it shows up on MainPath
MainPath attaches the certificate to the project’s domain, together with the DNS records under Domains.