Dipole-dipole and hydrogen bond intermolecular forces pull the ethanol molecules apart from one another.
Small alcohols have attached OH groups which make the alcohols polar.
The polarity of the alcohol and polarity of the water create intermolecular forces, most notably dipole-dipole forces.
The positive and negative dipoles in the molecules align, tugging at one another and causing the alcohol molecules to break apart from one another in the water and dissolve.
Especially notable in alcohols is the presence of hydrogen bonding, the strongest type of dipole-dipole forces that occurs between a hydrogen atom and either an oxygen, nitrogen, or fluorine atom.
The left shows the hydrogen bond attractions in a solutions of ethanol and water.