TBH is the acronym for, To Be Honest.
Similar slang and acronyms used on the internet include:
2BH stands for, to be honest.
FWIW that stands for What It’s Worth
IHDK stands for I honestly don’t know.
IMAHO stands for in my absolutely honest opinion.
JBH stands for just being honest.
JMHO that stands for Just My Humble Opinion
LBH stands for let’s be honest and loser back home.
MHO stands for my honest opinion.
OTHO that stands for On the Other Hand