Water activity, written aw, describes the availability of water in a food by comparing its equilibrium vapor pressure with that of pure water at the same temperature. It is not the same as moisture percentage: dissolved salt or sugar can bind water and change its availability.
Water activity influences microbial growth and texture. It requires appropriate measurement and cannot be judged by touch. Neither a low-looking moisture content nor a guessed aw value establishes that a homemade food is shelf-stable.
Reference: Further reading.