Is it safe to delete dummy tables Oracle 11g XE i created a database schema in 11g express edition, however there are some APEX tables and some dummy data...

Is it safe to delete them? also i would like to know what does apex means and why they have a dollar sign, thanks...

APEX$_ACL                      TABLE
APEX$_WS_FILES                 TABLE
APEX$_WS_HISTORY               TABLE
APEX$_WS_LINKS                 TABLE
APEX$_WS_NOTES                 TABLE
APEX$_WS_ROWS                  TABLE
APEX$_WS_TAGS                  TABLE
APEX$_WS_WEBPG_SECTIONS        TABLE
APEX$_WS_WEBPG_SECTION_HISTORY TABLE






I used SYS to create a new user, the new user was created along with a workspace and a database schema, please see the images above.
I wouldn't suggest removing those tables, no.  The Oracle XE browser-based interface is written in APEX (Application Express, a framework for developing web-based apps in the Oracle database).  If you break APEX, that interface will likely stop working.