It's a rather complex question to answer - not because I wouldn't know where to start, but because there are so many things to talk about (perhaps my approach is too biased by all the teaching and seminars that I hold regularly ...)
To make it simple and try to give you a perspective, I'd say that SEO stands for a number of issues today:
- Successful site architecture that ensures your website is built following search engine friendly criteria
- Quality Content - without it you're lost
- Organic link building - the art of building a solid and appreciated online reputation, a must these days if you wish to rank and stay ranked in the search engines
- Networking - how to build relationships with others and other websites
I've certainly gone beyond the typical SEO activities but these are the ingredients of a successful online strategy - more web marketing i your like, but my feeling is that professionals with enough experience are finding themselves more and more dedicated to web marketing efforts as traditional SEO expertise gains importance to Industry.
One last thing: be careful about listening too much to what is said in forums - it will take a lot of trial and error before you understand what works and what doesn't - if you are serious about learning, take a course and learn from an expert, then go into forums ;-)
Hope this helps, and have a great week end