SRL is what let's us run scar on an almost undetectable (if not completely) level inside of runescape. It is created by a team of good scripters who dedicate their time to making our autoing experience as undetectable as possible. All of the functions and procedures in SRL are color based.
SMART let's you auto with the runescape window minimized.
Reflection is the more accurate, but more easily broken engine. It reads directly from the SMART client, so that it can be 100% precise.
One last thing. I would suggest signing up at http://www.villavu.com/forum/index.php
. It's the official SRL forum, and has a gold mine of tutorials and examples, once you make ten non spam posts and are there for a week.
If you need any more help, feel free to add me on MSN.