env for terminal "basics what is some useful env i might use how would i use them "

TERM_PROGRAM=iTerm.app
TERM=linux
SHELL=/bin/bash
TMPDIR=/var/folders/_3/12dq_1xx1j1fgl9481zccnb40000gn/T/
TERM_PROGRAM_VERSION=3.4.9
TERM_SESSION_ID=w0t0p0:2A716BC0-911D-4DA6-85D4-C2D1F32F7D4C
USER=viper
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.iDB4QIjXr1/Listeners
__CF_USER_TEXT_ENCODING=0x0:0x0:0x0
PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Applications/Server.app/Contents/ServerRoot/usr/bin:/Applications/Server.app/Contents/ServerRoot/usr/sbin:/Applications/Postgres.app/Contents/Versions/latest/bin
PWD=/Users/viper
LANG=en_US.UTF-8
ITERM_PROFILE=Default
XPC_FLAGS=0x0
XPC_SERVICE_NAME=0
SHLVL=1
HOME=/Users/viper
COLORFGBG=7;0
LC_TERMINAL_VERSION=3.4.9
ITERM_SESSION_ID=w0t0p0:2A716BC0-911D-4DA6-85D4-C2D1F32F7D4C
LOGNAME=viper
LC_TERMINAL=iTerm2
COLORTERM=truecolor
_=/usr/bin/env

here are some of my env