Am I allowed to write about a discovery, while pending acceptance of my manuscript on the same topic? This year, I submitted a manuscript to a journal regarding new information uncovered on a particular topic. I am awaiting my reviews and a decision on its potential acceptance to the journal. 

The journal policy states that the manuscript has to be original content and not published elsewhere. By "not published elsewhere", does this also mean that I am prohibited from discussing the discovery publicly or in media until it is published in the journal (or any journal for that matter). If I write about the discovery (for example, in a newspaper), will this count as being "published elsewhere" - even if the news article and the manuscript are not the same?
This depends on the field and/or the journal. My understanding is glam-mags (Science, Nature) do indeed tend to prohibit any mentioning of the paper contents. On the other hand, for say mathematics journals it would be common to have a preprint on the arXiv anyway, so for something of particular interest, a lot of coverage can arise prior to the actual publication (see the proof of Kepler's conjecture for an extreme example).