This is a mnemonic for remembering most of the simple demonstrative and interrogative words in Japanese, which fall into a very nice and predictable pattern, as shown below. This is another example of the striking regularity of the Japanese language.

kore        sore         are	          dore
korera      sorera       arera         dorera
kono        sono         ano	          dono
koko        soko         asoko         doko
kochira     sochira      achira        dochira
konna       sonna        anna          donna
konna ni    sonna ni     anna ni       donna ni
koo	     soo          aa            doo

These words all involve concepts of relative distance. Ko- close, so- not close, a- far away, and the interrogative do-. Note that not all of these words can stand by themselves like koko or korera. The kono series require a following noun, as do the konna words. Also, according to two of my textbooks, dorera is deprecated.