Suboxides:

The oxides contains more oxygen atoms as compare to central atoms and according to valency requirements of central atoms number of oxygen atoms are not sufficient.

For examples B₂O₃, C₃O₂, C₁₂O₉, Pb₃O, Rb₉O₂, Cs₁₁O₃ etc. 

Mixed Oxides:

The oxides in which oxidation state of oxygen atom is found to be it's uncommon oxidation state on central atom. Mixed oxides on dissolving in water undergo "disproportionation" 

For examples B₂O₃, ClO₂, Cl₂O₇ , N₂O_{5 ,} As₂O₄ etc.

Related Questions:

Which oxides (Anhydrides) gives two Oxyacids in water ?

What are the structural difference between oxides ( P4O6 and P4O10) of phosphorous?

What are common structural features of oxides (P4O6 and P4O5) of phosphorous?

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