I'll make a list of root words and the words with prefix -ter.
Function: as superlative, the formula is = ter + root word (adjective)
-cantik (beautiful) = tercantik (most beautiful)
-pandai (smart) = terpandai (smartest)
-besar (big) = terbesar (biggest)
-baik (good) = terbaik (best)
Function: declares a condition, mainly composes a passive sentence, the formula is = ter + root word (active verb)
-buka (open) = terbuka (is opened)
e.g. Pintunya sudah dibuka / The door has been opened
-tutup (close) = tertutup (is closed)
-dengar (hear) = terdengar (is heard)
-kejut (surprise) = terkejut (is surprised)
Function: declares that an activity is done without prior intention, this mainly composes a passive sentence, the formula is = ter + root word (active verb)
-buang (throw away) = terbuang (is thrown away, without being realized before)
e.g. Uangku terbuang ketika aku membuang tas plastik. (My money was thrown away when I threw the plastic bag away)
-kunci (lock) = terkunci (is locked)