How can we diferentiate between strategic communications and strategic PR, corporate communications or integrated marketing communications?

Dear Chehou: In the United States, the overall category of corporate communications covers all areas of communication required by a medium to large-sized company.
Under the umbrella of corporate communications, you will typically find media relations (both production of press releases and the establishment of a media strategy), corporate speech-writing and presentations (to be prepared for the CEO, CFO, COO, etc.), production of the company's annual report, and production of any key public relations or marketing materials directed to a consumer audience.
Corporate Communications also covers the area of strategic communications, which means planning, typically in the form of annual, bi-annual and quarterly plans that address the company's key audiences and markets and that make sure that company communications are aligned with these plans.
"Strategic PR" refers to strategic media relations and community-building.
Again, these are areas that typically fall under Corporate Communications in a company.
In an advertising or PR agency, they may use these words to describe their services to companies.
Within a company's corporate communications function, I would assume that their PR practices are strategic, meaning that they support and enhance the company's overall strategic direction.
Strategic communications is similar to Strategic PR -- if being practiced in a company under the corporate communications umbrella, I would hope that their communications practices -- all of them -- are strategic, meaning matching the company's overall strategic direction.
If not, they're missing the boat and need someone to help them with their planning! Integrated Marketing Communications includes the overlay of marketing practices to communications.
Typically, this means the production of marketing materials such as brochures, advertising, a consumer or business to business-directed web site and social media that promote particular products and services, etc.
It can also include specific product PR such as press releases to trade media, in concert with an overall marketing plan that directs the placement of product/service promotional campaigns/launches.
I hope this helps - if you have any other questions, please feel free to contact me.
Regards, Betsy Richman

It's so more than helpful and I am so glad, thank you very much.

Strategic communication can mean either communicating a concept, a process, or data that satisfies a long term strategic goal of an organization by allowing facilitation of advanced planning, or communicating over long distances usually using international telecommunications or dedicated global network assets to coordinate actions and activities of operationally significant commercial, non-commercial and military business or combat and logistic subunits.
It can also mean the related function within an organization, which handles internal and external communication processes.
Strategic communication can also be used for political warfare.