This topic introduces basic concepts and terms used in Alibaba Cloud SSL Certificates Service.


NGINX is a lightweight web server and processes highly concurrent connections. You can configure it as a reverse proxy server or an email proxy server that complies with Internet Message Access Protocol (IMAP) or Post Office Protocol version 3 (POP3). NGINX is based on BSD-like licenses. NGINX runs on different operating systems, such as Linux, Windows, FreeBSD, Solaris, AIX, and macOS. It can be used for reverse proxy, load balancing, and dynamic and static separation.


Tengine is a web server project initiated by Taobao. It supports all the features of NGINX and is compatible with NGINX configurations.


PuTTY is connection software that allows you to perform operations by using Telnet, SSH, rlogin, pure TCP, and serial interfaces. It can remotely manage Linux and Windows operating systems.


Xshell is a powerful terminal emulator. It supports Telnet on SSH1 and SSH2 clients and also in Windows. Xshell can remotely manage servers that run different operating systems from Windows. Xshell supports VT100, VT220, VT320, Xterm, Linux, SCO ANSI, and ANSI terminals and provides a variety of terminal screen views to replace traditional Telnet clients.


CentOS is an enterprise-grade Linux distribution and is derived from the sources of Red Hat Enterprise Linux. It is open source and free of charge.


A certificate signing request (CSR) file contains your server and company information. When you apply for an SSL certificate, you must submit the CSR file to a certificate authority (CA). The CA signs the CSR file by using the private key of the root certificate and generates a public key file to issue your SSL certificate.