Dear Student,
Siloxanes are the compounds, linear or branched, containing alternate silicon-oxygen atoms in backbone with alkyl group or hydrogen as other groups attached to silicon atom. These alkyl groups can be same or different in a single siloxane.
Silicones are the polymers with siloxane units as monomers. These are formed by linking the siloxanes and have alternate silicon-oxygen atoms in backbone and alkyl groups as other groups bonded to silicon atom.
Regards.