Samurai X is indeed
Rurouni Kenshin, but X is a different series than the one involving the Meiji Era. It is in fact a
prequel, in which the origins of Kenshin's
skills in the Hiten Mitsurugi style, and his efforts to
dethrone the Tokugawa Shogunate are explored.
As the show is an OAV (or OVA), the quality of the animation is much better than the original anime series. As the animation in the original series is excellent, this is saying a great deal. The OAV series is regrettably only 4 episodes long.
The events in X are of a very serious nature, with a historically accurate bent. The levity of the original Kenshin series is nowhere to be found in X. Blood, death, and the hard choices Kenshin must make on a day to day basis are the main focus of this series.
Samurai X is also the name of a Kenshin movie, based in the Rurouni Kenshin timeframe. It is being released in the United States this year.