The term "professional writing" commonly refers broadly to texts written for business purposes such as business letters, reviews and recommendations, feasibility studies, progress reports, and application materials. In turn, "technical writing" refers to documents that often explain technical processes or explain how to do something, such as technical descriptions and instructions and process reports.
Professional and Technical Writing texts share many similarities with traditional academic writing genres, such as an emphasis on clarity, succinctness, and thesis-driven, deductively organized texts. The skills you learned writing expository, persuasive, and argumentative documents serve as a useful tool chest for workplace documents.
As business and industries reshuffle communication practices to engage the "wisdom of crowds," professional and technical writers need to become more and more savvy of new media technologies. Increasingly, therefore, writers in professional and technical settings are experimenting with new genres. They also tend to be concerned with re-mediating content--republishing, for example, the press release as a tweet, podcast, videocast, news report, and blog.So what distinguishes professional and technical writing from more traditional academic genres? One primary distinction is audience: academic writers tend to write to other academic writers, either peers or teachers, whereas technical writers are usually writing to more narrow audiences, which often means that technical writers need to work really hard to simplify complex topics. In this way, technical writers work more as translators, working from the complex to the simple while academic writers, particularly when writing for professional journals, may pitch content at a higher level, assuming a greater knowledge base on the part of their readers. For example, when writing instructions a technical writer can't assume knowledge of terms and tools. Additionally, professional and technical writing genres tend to avoid long blocks of texts. Visual design is a big deal in technical communication environments.