Is luajit Suricata necessary when installing Sricata

i have to install suricata on Debian 8.6 Jessie and i’d like to know whether LUAJIT is necessary and what is the objective of LUAJIT. The doc doesn’t mention anythnig about LUAJIT.
is it the same as YAML?
is it obsolete?
i see a variable set to NO when i launch suricata --build-info