A Quick Note about Prefixes

Actually, the word means "thing." This word is given a prefix:

이- this (near to speaker)
저- that (far from speaker and listener)
그- that (near to listener), or
"that" which was mentioned in a previous sentence

These prefixes are called determinatives by linguists, because they help you determine where something is in relation to you. You can attach these prefixes to any noun; for example:

이책 this book [here]
저나무 that tree [over yonder]
그학교 that school [we were talking about]