GRASS (short for “Geographic Resources Analysis Support System”) is an open-source geospatial software for raster and vector data processing and analysis. There is nice overview of GRASS features on the GRASS website, in case you are not familiar with it.
Newly, GRASS daily development snapshots can be directly installed via conda1 into a conda environment on all major platforms (Linux, Mac OS, and Windows) – no manual setup required, which streamlines the installation process.
While part of GRASS functionality is also available through QGIS (via the GRASS provider/plugin and via the Processing toolbox), installing GRASS directly (through conda or the other channels) allows anybody to access the latest features and updates directly from the GRASS development team as well as to use user-contributed add-ons that may not be directly available in QGIS.

Footnotes
A cross-platform, open-source package and environment management system widely used in the data science and scientific computing ecosystems.↩︎