What do these two computer-tech terms mean?

[husoski]

"hash" is a nickname for the # pound/number symbol, going back to at least the early 70s. A tag name beginning with # (at Twitter) was then called a "hashtag". Now, it's easy to find "definitions" that suggest at least that the # is a "hashtag symbol" or just a "hashtag". Pretty soon, if not already, that will be the "official story" and the real origin lost. Like with "hacker".

"Retina Display" is Apple's name for the ludicrously-high-resolution display on the latest iPad, iPhone and macBook models. Probably iMacs too, soon.

"Google", "Yahoo!", "AltaVista", "Ask.com" are example of search engines. You can find the answers to questions like these easier and quicker than asking here.

Edit: See what I mean? Before I even hit Submit, someone has already posted that "#" is a "hashtag". One thing you can do a search for that hasn't changed meanings yet is "Eternal September".