Tenacity comes with a variety of features out-of-the-box:
Recording
Record audio from various audio devices (real or virtual)
Export & Import
Work with a wide range of audio formats (extendible with FFmpeg)
High Quality
Work with stellar quality options, including up to 32-bit float audio support
Plug-Ins
Import plug-ins to aid your workflow, with support for VST, LV2, and AU plugins 
Scripting
Use the built-in scripting language Nyquist, or import with Python, Perl and other languages with named pipes
Editing
Use a variety of editing options, such as arbitrary sampling and a multi-track timeline
Accessibility
Accessibility features include editing via keyboard, screen reader support and narration support
Tools
Use a variety of analysis tools for signals, including audio
Tenacity vs. Audacity
Tenacity is not merely an Audacity fork that removes error reporting and update checking, although it might seem like it. Tenacity utilises its own features and fixes, including the following:
- New, modern themes.
- Improved support for more platforms such as Haiku.
- Matroska importing and exporting without needing FFmpeg.
- Support for importing, editing, exporting Matroska chapters as label tracks.
- Sync-lock improvements, including the ability to temporarily override sync-lock.
- Horizontal scrolling in the Frequency Analysis window.
- Under-the-hood changes, such as a revamped build system allowing for modern upstream dependencies.
For further information, see this comparison page.