Lamport's last version of LaTeX (LaTeX 2.09, last updated in 1992) was superseded in 1994 by a new version (LaTeX2e) provided by the LaTeX team. LaTeX2e is now the only readily-available version of LaTeX, and draws together several threads of LaTeX development from the later days of LaTeX 2.09.
LaTeX2e has several enhancements over LaTeX 2.09, but they were all rather minor, with a view to continuity and stability rather than the "big push" that some had expected from the team. LaTeX2e continues to this day to offer a compatibility mode in which most files prepared for use with LaTeX 2.09 will run (albeit with somewhat reduced performance, and subject to bitter complaints in the log file). Differences between LaTeX2e and LaTeX 2.09 are outlined in a series of 'guide' files that are available in every LaTeX distribution (the same directory also contains "news" about each new release of LaTeX2e).
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=latex2e