The original Greek word used in Matthew for the word Hell is
Original Word: γέεννα
Part of Speech: Noun, Feminine
Transliteration: geenna
Pronunciation: gheh'-en-nah
Phonetic Spelling: (gheh'-en-nah)
KJV: hell
NASB: hell
Word Origin: [of Hebrew origin (H1516 (גַּיא גַּי - valley) and H2011 (הִנּוֹם - Hinnom))]
Meaning
1. valley of (the son of) Hinnom
2. ge-henna (or Ge-Hinnom), a valley of Jerusalem,
{used (figuratively) as a name for the place (or state) of everlasting punishment}
It's a place with a fire that can destroy both body and soul as the verses says,
MATTHEW 5:22 (KJV)
But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of HELL FIRE.
MATTHEW 10:28 (KJV)
And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to DESTROY BOTH SOUL AND BODY IN HELL.
And that fire can't be quenched
MARK 9:43 (KJV)
And if thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into HELL, into the FIRE THAT NEVER SHALL BE QUENCHED: