Molality is moles of solute per kg of the solvent.
#m = "Moles of solute"/"Mass of solvent in kg"#
For example, 1 molal is 1 mole of solute in 1 kg solvent.
Now for your question,
When you say that molality of a solution is 0.1, it means 0.1 moles of solute are dissolved in 1 kg of solvent