Certbot is an easy-to-use client that fetches a certificate from Let’s Encrypt—an open certificate authority launched by the EFF, Mozilla, and others—and deploys it to a web server.
Certbot and Let’s Encrypt can automate away the pain and let you turn on and manage HTTPS with simple commands.
Certbot is a fully-featured, extensible client for the Let's Encrypt CA (or any other CA that speaks the ACME protocol) that can automate the tasks of obtaining certificates and configuring webservers to use them.
Instructions on the Internet, and some pieces of the software, may still refer to this older name.
For instance, if you want to obtain a cert for example.com, www.example.com, and other.example.net, using the Apache plugin to both obtain and install the certs, you could do this: (The first time you run the command, it will make an account, and ask for an email and agreement to the Let's Encrypt Subscriber Agreement; you can automate those with --email and --agree-tos) If you want to use a webserver that doesn't have full plugin support yet, you can still use "standalone" or "webroot" plugins to obtain a certificate: To understand what the client is doing in detail, it's important to understand the way it uses plugins.