Hello!
After the addition of the last two teaspoons of salt, the solution is saturated
A solution is saturated when it has the highest amount of solute (in this case the salt) that the solvent (in this case the water) can dissolve at that pressure and temperature.
Visually, a saturated solution can be detected when the adding of more solute results in the settling of solute grains (in this case salt) at the bottom of the container, because the solvent couldn't dissolve them at that pressure and temperature. That's why we can say that the solution is saturated.
Have a nice day!