While position and post can often be used interchangeably in reference to employment or occupation, I believe
- Post more strongly connotes an assigned station, especially a specific geographic place and often for a temporary or rotating assignment.
- Position on the other hand more strongly connotes a rank or class.
In my experience, if you ask an executive for her post, she may say "the Lisbon office," whereas if you ask for her "position," she's more likely to say "Vice President for Ibero-European Operations" or some such.
Both position and post can trace their roots back to the Latin verb pono, ponere, meaning to put or to situate something, but the latter, according to Merriam-Webster, came via Middle French and Old Italian having acquired the meaning of a relay station along the way. This sense of post is of course carried through in its courier-related meanings, i.e. we send mail through the post (NAmE) or send a post through the mail (BrE).
The U.S. Army refers generically to its installations as "posts," and a soldier is "posted" to a particular assignment as well as given a particular "post" when on duty. In the same way we can speak of journalists or diplomats being sent to a "post" like the Tehran bureau or the Shanghai consulate or of waitresses or warehouse workers being sent to a "post" like tables 20-24 or delivery dock C. In both cases, we are speaking of a temporary assignment to a particular station.
So in your example, I would think either of
[He] applied for the position of head of human resources at [a big company].
[He] applied for the post of head of human resources at [a big company].
to be fine, the former preferred if "head of human resources" is a permanent role, the latter if it's a waystation for those on their way up or down the corporate ladder.
My understanding is that in contrast is used to, well, contrast two ideas, or compare their differences. This does not imply that either idea is wrong, just that the two are contrasted.
"Kimchi is a Korean dish that is popular among millions. In contrast, many complain that it tastes like rotten cabbage".
The viewpoints are contradictory, but neither is necessarily correct.
On the contrary, however, is used when the writer or speaker wishes to emphasize a negative claim - that is, he brings a viewpoint that is explicitly not accepted, and the phrase is used to bring the alternate option:
"Kimchi's flavor is not rotten and naueseous, as some claim. On the contrary, it is a delightfully playful dish".
Best Answer
Short answer: no conferences belong in conference rooms. Meetings you can potentially have anywhere.
conference from Latin conferre (bring together)
which is almost the same like meeting
Meeting is more of an encounter.
A conference (a bringing together) implies more effort. Usually a conference also takes longer than a (relatively quick) meeting.
So a meeting room might just be a simple room for a quick meeting. (all meeting rooms these days, at least at my workplace, seem to have conference capable phones in here anyway, so the distinction is blurry)
A conference room might be more sophisticated with video conferencing equipment or dedicated presentation facilities.
You can have a meeting in a conference room, as you can meet in any other room say the kitchen or bathroom.
You could also have a conference in the canteen, or the bathroom even though I don't think that is considered best practice.
So having a conference in a meeting room might not make sense, since the meeting room might be to small and lack the proper equipment. Speaker facilities, video conferencing facilities.