These are the same things you can get from any learning tool, be it a book, a seminar, or a school course. All three are necessary for learning but the most useful is the how.
This is how I define each of those words, with regard to seminars:
Why: why are you in this seminar, why you should pick this seminar over others, why invest in [fill in the blank]. This is the motivator. It is both the sales pitch for whatever product they are selling (if you don't know that they are selling a product, you haven't been paying attention) and it is a call to pay attention and learn something. If you don't have a strong why, you'll never succeed. If you don't have a strong why, then why bother? Also, if you don't know what you want to do, the why can let you know if the topic is for you or not.
The Why question is necessary and the first question that needs to be answered in a seminar but it is also the most trivial. If this is all you get out of a seminar, it better be a free seminar. Even if it is a free seminar, if you don't get more than this, you are in for a long ride, generally paying for ever more expensive levels hoping to get some useful information eventually.
What: This is where they tell you what you should do. This will be things like: buy zero down, buy low and sell high, buy foreclosures, buy probate property, buy/sell on eBay, etc. These are the strategies. You need to pick a strategy so you can focus your efforts to accomplish your goal.
A number of presenters will act as if they are giving real information here but it is not as helpful as they make it seem. These are the fortune cookie answers. Yes, I should buy low and sell high, now what. This kind of information can be deceiving. There are multiple levels of "What" and some seminar chains just give more detailed levels of "What" as you pay for more expensive levels of seminar. If you don't get some "What" in even a free seminar, stay away. If you payed more than $1000, don't be satisfied with "What."
Don't get me wrong, you can learn a lot from these seminars but you will have to a lot of homework and figure out a lot on your own. That brings me to:
How: This is where they get into the details of how to implement the strategy. It is where they show you how to go to the courthouse and what information to look for, what signs to put in front of your house, what ads to place and when you should place them. This is what you are going to the seminar for. The main question is how many levels of seminar you'll have to go through to get this.
If you get some of the "How" at a free seminar, you will generally get more at the next levels. The difference will be between being able to accomplish the task at all and being able to excel at it.
Some presenters have a variation of this: They give the "What" and sell a utility or service that takes care of the "How." This can be useful but it isn't as good as getting the "How" and getting the utility. If the market changes and you know the Why, What, and How, you can make adjustments to fit the new market. If you just know the Why and What with a utility to take care of the How and the market changes, you will then have a useless utility.
Don't expect a presenter to give away all their secrets at a free or low cost seminar. However, you can use what they tell you at the free seminar to predict their behavior at later seminars.