Tera Term (rarely TeraTerm) is an open-source, free, software implemented, terminal emulator (communications) program. It emulates different types of computer terminals, from DEC VT100 to DEC VT382. It supports telnet, SSH 1 & 2 and serial port connections. It also has a built-in macro scripting language (supporting Oniguruma regular expressions) and a few other useful plugins.
The first versions of Tera Term were created by T. Teranishi from Japan. At the time, it was the only freely available terminal emulator to effectively support the Japanese language. Original development of Tera Term stopped in the late 1990s at version 2.3, but other organizations have created variations.
In October 2002, Ayera Technologies released TeraTerm Pro 3.1.3 supporting SSH2 and added multiple other features like a built-in web server for API integration with external systems, recurring "keep-alive" commands, and ODBC database support via the TT Macro Scripting Language. Ayera Technologies did not make their source open, but does provide limited technical support.
In 2004, Yutaka Hirata, a software designer from Japan, restarted development of the open source version of Tera Term. He added his own implementation of SSH2 and many new features on top of what was part of version 2.3. A complete list of them is published on TeraTerm Document.
To avoid confusion with version numbers and to indicate that Tera Term developed by Yutaka was more recent than version 3.1.3 from Ayera Technologies, it was decided to give this branch of Tera Term Professional version numbers starting 4.xx.
In January 2005, Boris Maisuradze, together with Yutaka Hirata, started the TeraTerm Support forum where they answer questions from Tera Term users. Posting in this forum is the best way to suggest new features for Tera Term or propose new commands for the Tera Term Macro language.
Since 2007, Tera Term has been maintained by Tera Term Project (Japanese Developer team) as open source software.
Tera Term has comparable features to PuTTY and SecureCRT.