Grotesque fonts

Today while reading this page: Roboto: Google’s signature font is now open source, I saw this comment, in response to someone asking what is so special about this font, Roboto.

I don't know specifics about this particular typeface (and I haven't been "into fonts" for a while), but Roboto is pretty much another typeface with some Grotesk (e.g. Helvetica) lineage.

Who would name fonts grotesque? My knowledge about fonts begin and end in discerning them as serif and sans serif. Wikiepedia says :

Akzidenz-Grotesk is a grotesque (early sans-serif) typeface originally released by the Berthold Type Foundry in 1896 under the name Accidenz-Grotesk. One of the first sans serif typefaces to be widely used, its design influenced many later neo-grotesque typefaces after 1950.

Grotesque is a subcategory of sans serif fonts (they are grotesque, neo grotesque, humanist and geometric). It is not clear for me what is the defining characteristic of a grotesque font, even after reading those description; I can't identify a font by looking at it as grotesque or humanist, these categorisations more or less appears arbitrary to my untrained eye.

You can kill yourself with a 9 V battery … or things I learnt this week

1. You can kill yourself with a 9 V battery,  the ‘real’ story of an unfortunate American sailor. This is surprising and I didn’t knew this earlier. I used to put the 9 V battery on my tongue to feel the current. Found the link from a Slashdot discussion in At Oxford, a Battery That's Lasted 175 Years.
2. Taking notes on a laptop is less efficient than writing with pen on paper. It is, in fact, detrimental to learning!  This has to do with the speed at which writing notes using a pen and a laptop differs. Writing long hand is slow and will force the note taker to summarise the information he is receiving; laptop note takers often copy sections verbatim from the source, which requires less thinking. ‘I had the sense that their brains were less engaged and that they were acting more like stenographers than students.’
3. On Winston Churchill’s ninetieth birthday thousands of greeting cards were sent, addressed to ‘The Greatest Man in the World, London’, and they were all delivered to Churchill’s home.