What I aim for is
gross oversimplification with the information players need to
create a character. This usually means just a few paragraphs about the setting, the current political situation, and how that relates to the PCs (including PC motivation, and class/race options).
This is easier to explain via an example:
You are part of a rebel group, trying to free the people from the oppression of the cruel Prince John, who has usurped power from the true king. Political turmoil and war abroad have created instability among the Lords and Ladies of the kingdom, creating an opening for the Prince to seize power while the king is fighting overseas. Now the Prince is cracking down on those disloyal to him, punishing and tormenting the common people.
But a secret rebellion has sprung up against this tyranny. Your reasons for joining the rebellion may vary (defending the weak, loyalty to the true king, personal vengeance against the Prince, or maybe you are just seeking excitement and glory), but your mission is the same: undermine the Prince's power, thwart his schemes, and aid the common people who he has enslaved. Right now, the rebellion lacks the political support to act openly, but instead engages in guerrilla warfare and subterfuge.
The rebels are headquartered in Sherwood Forest, a wilderness area rumored to be haunted (rumors which the rebels themselves encourage). The nearest big city is Nottingham (the "h" is silent), capital of a small region known as Nottinghamshire, a rolling countryside of farms and fields that produces much of the grain, wool, and beer for the kingdom. The common folk of Nottinghamshire are known as good-natured and loyal, but somewhat superstitious. Unfortunately, the region is ruled by a corrupt Sheriff and his brutal enforcer, Sir Guy Gisborne.
The state religion is simply called the Church, an organized religion that is officially monotheistic, but venerates numerous Saints who fulfill a role analogous to gods in other D&D settings. Of course, some people still secretly worship the polytheistic Old Gods, a crime punishable by death. If you're playing a cleric or other religious character, feel free to make up whatever Saints or Old Gods you want for your character.
Any race or class is allowed, but this is a very low-magic, human-centric setting, so if you're playing a spellcaster or a demi-human, expect to get some weird looks and maybe be subject to curiosity and awe. Particularly exotic demi-humans (tieflings, dragonborn, tabaxi, goblins, tritons, etc.) are advised to wear disguises or at least a hooded cloak; you may be met with fear and distrust by the very people you are trying to help! Most monsters and magical creatures are only found in remote, isolated areas, or in the Otherworld (a sort of combination of Feywild and Shadowfell, depending on whether you're in the happy part or the scary part). Full spellcasters are rare, but not unheard of. They are often regarded as powerful but dangerous allies.
Now, we could go into a LOT more detail about the kingdom and its thousands of years of history and culture. Or we could get into the nuance of whether or not the Prince is actually a cruel tyrant, or just caught in the middle of a power struggle. Or we could define the pantheon of Saints more precisely, or maybe even name and describe all the known spellcasters in the setting.
But, none of that is really needed to make a character and start playing. So don't even mention it.