Selenous acid is a weak acid. It can be heated to make selenium dioxide. It is more stable than sulfurous acid. It can be crystallized as a white solid. It is a weak oxidizing agent. It reacts with bases to make selenites.
It is made by dissolving selenium dioxide in water.
It is used in the bluing of steel. It is used in the making of organic compounds.
Selenous acid is very toxic. Just ingesting a small amount can kill you.