Most often These look as overlapping topics. Can anybody help me to figure out?
"If Information Architecture is the spatial side of information, I see content strategy as the temporal side of the same coin." - Lou Rosenfeld
This article nicely explains the difference between content strategy and IA. In short,
Content strategy focuses on the delivery, governance and planning content creation.
Information Architecture deals with the design of an information space and to ensure that users can easily find what they’re looking for.
Information architecture is, like civil engineering architecture, an art and craft of making the system easier and more intuitive to navigate. This includes, among other things, making sure that the structure of the system/service is compliant to normal human heuristics and common standards. So that if user is looking to change their password, they find it in "Settings", and not in "About".
Content strategy, like interior & exterior design, is about preparing the best filling for this system and it's marketing channels.
Strategy part means that the information filling will be thought through, scheduled and prepared for automatic distribution in advance and in line with some unifying idea that corresponds to the values of the system itself.