What is the difference between LANG="pl_PL.UTF-8" and LANG="pl_PL ?

Issue

• On two servers default system language is polish. But there is one difference in them, on first server locale env is as follow

# locale
LANG=pl_PL
LC_CTYPE="pl_PL"
LC_NUMERIC="pl_PL"
LC_TIME="pl_PL"
LC_COLLATE="pl_PL"
LC_MONETARY="pl_PL"
LC_MESSAGES="pl_PL"
LC_PAPER="pl_PL"
LC_NAME="pl_PL"
LC_ADDRESS="pl_PL"
LC_TELEPHONE="pl_PL"
LC_MEASUREMENT="pl_PL"
LC_IDENTIFICATION="pl_PL"
LC_ALL=

# cat /etc/sysconfig/i18n
LANG="pl_PL"
SYSFONT="latarcyrheb-sun16"

and on the second server we see:

LANG=pl_PL.UTF-8
LC_CTYPE="pl_PL.UTF-8"
LC_NUMERIC="pl_PL.UTF-8"
LC_TIME="pl_PL.UTF-8"
LC_COLLATE="pl_PL.UTF-8"
LC_MONETARY="pl_PL.UTF-8"
LC_MESSAGES="pl_PL.UTF-8"
LC_PAPER="pl_PL.UTF-8"
LC_NAME="pl_PL.UTF-8"
LC_ADDRESS="pl_PL.UTF-8"
LC_TELEPHONE="pl_PL.UTF-8"
LC_MEASUREMENT="pl_PL.UTF-8"
LC_IDENTIFICATION="pl_PL.UTF-8"
LC_ALL=

# cat /etc/sysconfig/i18n
LANG="pl_PL.UTF-8"
SYSFONT="latarcyrheb-sun16"

• What is the difference between this settings ?