Lamport's last version of LaTeX (LaTeX 2.09, last updated in 1992) was superseded in 1994 by a new version (LaTeX2e) written by the LaTeX team.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). Differences between LaTeX2e and LaTeX 2.09 are outlined in a series of 'guide' files that are available in every LaTeX distribution; the most important of these files is available on the Web as http://www.tex.ac.uk/tex-archive/macros/latex/doc/html/usrguide/ and outlines the differences as seen by the ordinary writer of documents and of simple macros.