Abstraction is simply a way of modelling entities by focusing on the important attributes and suppressing the less important details.
This means as decomposition proceeds, the design of components is expressed gradually in more concrete terms until at the lowest level of abstraction when the design is ready for translating into some programming language.
Information hiding is when the modules sh'd be characterised by design decision and each, hiding information from all the others.
i.e each info in each module sh'd be hidden or not accessed by other modules that don't need it.
Hope this info. helps u.