The dark priesthood of the marketing cult will talk a lot about target audiences for a product: Who is intended as the buyer of the widget you are trying to sell? Obviously a commercial product needs to have some sort of audience that is willing to exchange money for goods and services.

With tabletop gaming the broadest possible audience is "tabletop gamers". In theory every person that plays a tabletop game is a possible buyers. (people who don't play tabletop games are also possible buyers but that is a lot less likely in the indie publishing sphere). 

Of course many tabletop gamers are not inherently going to be interested without some persuasion, personal interest or temptation. The RPG folks are not typically into hardcore naval warfare simulations and the euro board gamers probably don't want to make too many morale checks. Even within the miniatures gaming community your choice of theme or setting will narrow the field more. A WW2 game will obviously appeal primarily to people who are interested in that conflict (though converts can be had if you are clever or have nice presentation). 

Within that specialisation, things continue to break down in smaller groups: A game intended for beginners may appeal to a veteran that would like a more casual experience at times and will do better at drawing in interested, but inexperienced, gamers. A game that aims at experienced players will appeal more widely to people with extensive gaming experience in the period, but may find it more difficult to gain crossover appeal and converts (though not entirely: Some people know they want a hardcore experience from day 1). 

The rules themselves will also affect who might be interested. A lot of successful rules fall into what I call "one clever thing": The game rules are mostly very conventional but have one or two clever bits to make them stand out. Chain of Command fits this bill by having very conventional combat mechanics (roll to hit, roll for effect) but having a very clever turn sequence and patrol phase. 

Some games rely on strictly conventional mechanics throughout and while they will often not appear very exciting, they offer a solid experience that is easy to get into. Rapid Fire might serve as an example here which has remained a popular game at conventions for a lot of years. They also benefit from making it easier to adapt scenarios.

On the other end of the scale we have very "clever" games with unique mechanics such as Crossfire or my own Five men at Kursk. These games tend to attract very loyal audiences but because they are very radical in their assumptions they can also deter players looking for a more conventional approach.

Some settings lend themselves to a fair bit of tech nerd content (detailed tank lists, stats for 200 different variations of French line infantry etc.) which will appeal to certain gamers but overwhelm others. 

Even something as seemingly minute as the writing style might affect who gravitates towards your game. A more casual style may seem more welcoming but could also seem less professional. An abbreviated style appeals to those who prefer simplicity but may deter players who want thorough explanations. A "British" approach where things are left somewhat open to interpretation can act as both a selling point and a criticism depending on the audience.

These are all just examples and you can no doubt think of a dozen more. My point with today's ramble is that almost every choice you make during your design will influence how particular audiences and groups will respond to your game. That makes it worth sitting down and thinking about before and during the process. You might even write out on an index card (or on page 1 of your word processor file) who you are expecting to purchase it so you can refer back to it.