This is the first in a series of primers.  I hope it helps!

You’re missing the point, if you treat customized draft sheets like just any rankings list.

At Subvertadown, the main tool for draft assistance is TapThatDraft. On the one hand, the output might look like other lists. Especially the free 1-pager version (“Hold-My-BeerSheets”) looks similar to rankings you find elsewhere.

However, there’s a lot going on beneath the surface. And if you don’t treat it like a customized list, then you’re definitely not getting the main advantages.
So let’s cover the basics, so you can feel a lot better about your draft!

What it’s about.
Tools like TapThatDraft generate player “draft values” tailored for your situation. 
While other information also appears on the sheets, the main purpose is to gain an edge over your league mates by using these customized “draft values”.

• Does your league have 8 teams or 16? 

• Do your rosters have 1 flex spot or 3?  

These factors matter for improving your odds.  Your settings matter for questions like “Do I take QBs earlier or later?” 
So the purpose of these tools is to apply a methodology, to try and solve questions like these. 

How does it work? 
The tool first takes in fantasy player forecasts. Then it processes the data using your settings. Finally, it converts all of it into “draft values”. 
These numerical ratings are especially useful because they help you prioritize picks across different positions.
Overall, the point is this logical quantification can help to maximize the numerical worth of your final roster.

How do these values help with strategy? 
The easiest example is with auction drafts. 
The generated “values” of each player get directly converted into a suggested auction price. This direct conversion is a really nice feature of the theory!  It means we’re representing “expected worth”— the balance of supply and demand. This is what makes it a logical starting point, when you need to manage your budget.

What about for snake drafts? 
The numbers definitely help for snake drafts, too.  The “auction ordering” is already decent for applying to snake drafts, although it isn’t theoretically “optimal”.  To get even greater advantage in a snake draft, TapThatDraf additionally apply a concept similar to one known as “VONA”.  That basically means looking ahead in the draft upcoming, to make sure you’re not missing out. In other words, scanning ahead in a sequential draft helps to re-prioritize your picks, by accounting for expected drop-offs in positional value.

Why are people talking about positional scarcity? 
Positional scarcity is one of the key factors that’s addressable by the calculations of Value-based drafting.
First, there’s the core idea that some fantasy positions are just worth more—depending on your league size and settings—because there simply aren’t enough good prospects at a certain position.  
But the other important idea is that positional scarcity changes, during your draft.  As players get taken off the board, there can be significant drop-offs in value remaining. 
TapThatDraft addresses this in different ways, for auction drafts and snake drafts.

Be aware of the pitfalls of Value-based drafting!

At first, Value-based Drafting might sound like such an appealing idea, so we should optimize the heck out of everything! 
But let’s take a moment to ground things, because these types of tools can get “overdone”.

1. You can’t know the “true value” of any player. We can only make a best guesses at how they’ll perform, in advance of the chaotic fantasy season.

2. Secondly, don’t go taking the numbers too seriously. You might be taking things too far if you’re just blindly following the math and chasing mere decimals.

3. Remember: Ultimately, so much fantasy football success comes from picks that were plain lucky. In the best case, you might imagine making great picks by studying the tiny chances for players to achieve enormous upside.  Either way, just remember that our “best guess at player worth” can be faulty.

Summary

The point of VBD tools is to make customized ranking lists and player values. The purpose is to tailor player prioritization to gain the best advantage, in consideration of your specific league settings.