Enterprise was after? Last night I saw a Star Trek TNG episode that I believe was titled " The final frontier" where crew members of the Star Trek TNG used the holodeck to visit crew members of Star Trek Enterprise. How is this possible?

Star Trek TNG started September 28, 1987 and ended May 23, 1994

Star Trek Enterprise started September 26, 2001 and ended May 13, 2005


This has really confused me can someone please explain.