Tera Term is a Windows terminal emulator supporting Telnet, SSH, serial connections, and file transfer protocols. It features a plugin system (TTXSamples) for extensibility, a macro language for automation, and extensive configuration options. The architecture is modular with core terminal emulation, SSH implementation (ttssh2), macro interpreter (ttpmacro), and plugin loader. Key external dependencies include Windows API, OpenSSL/LibreSSL, zlib, Oniguruma, and Argon2. The project is actively maintained with recent commits and supports both legacy and modern Windows versions.