I am also one of those players and I'd be happy if you verbally told me the information. However I'd want to know the region we're starting in, what races are located there, what their place and culture is, their regional (and racial) history and what gods are worshiped by those who live in the starting region and what their creeds are and how their followers carry out their worship.
I am going to want to know the same, but to make a informed choice, I am going to want more than a specific region (if, by that, you mean a specific nation). For instance, my main homebrew setting for part of 1e through 3e has, 11 human nations, 3 elf nations, 7 Dwarf clans (1 of which was driven out of its home by an ancient dragon and for the past two hundred or so years were living in the swamp region of a human theocracy (now, they are battling the human theocracy which has claimed that land after the dragon was slain)), 1 gnome homeland, 1 halfling region, and 2 lizardmen "nations" (one is a sun-worshiping civilization while the other is comprised of peaceful plains-dwelling hunter-gatherers). 2 of the human nations, 1 of the elf nations, and the plains-dwelling lizardmen practice shamanism exclusively. 3 of the human nations are polytheistic, but there are a few witches and shamans worshiping a deity in one of her older aspects. The rest of the cultures are exclusively polytheistic.
For players, I can tell which classes or class variants are found (or not found) in a given culture or want certain organizations are like. For example,
1) I can tell players which cultures have the standard raging barbarian and/or the crafty hunter barbarian (some switch out archery or two-weapon fighting for other styles) as well as starting cultural weapons and armor (For urban areas, there is the "urban" barbarians".
2) For the players of clerics, I can present the player with a list of deities including their domains, tenets, the planar ally (including lesser and greater), adornments, holy symbols and tailored spell list associated with each deity. If they are interested, I know the high priests/priestesses of the major temples
For the cultures I have a list major NPCs (e.g., kings,/queens/jarls/other rulers, high priests/priestesses of the major temples, heads of the wizards' guild/academy, major wizards outside the guild (most of whom have been assassinated in recent history), head of the major noble houses for one of the countries, head of the two major thieves guilds, etc). In addition, there are things like cultural views of descent, marriage patterns, naming conventions (with examples), social mores, and views of punishment (e..g, banishment, imprisonment, cutting off limbs, shunning, cleansing rituals, etc.) . I can also tell players major monsters inhabiting the areas around their homelands depending upon region as well as known prestige organizations.
So essentially, characters can start from any of the cultures and the players can know about them at the start. Every one gets a 1-2 page hand out with a brief overview of the setting including races and one or two sentences about the culture. Each culture has a 1 to 2 page write-up. Certain organizations have another 1 to 2 page write-up (the second is usually a tailored spell list for clerics). Those are the the setting rules. There is also a list of house rules. Whether I go over this verbally with players or a player reads through the hand-outs does not matter (but handouts are helpful to ensure the players follow specific things like tailored spell lists)
Now, I don't expect DMs to go quite as in-depth, but a lot the above are things that I think should be worked out before character generation to give players like me an understanding of the setting and allow us to make informed decisions about the campaign and make an informed decision about participating.
