Here is an idea for introducing new players to a game world.
A bright flash and your eyes slowly adjust to the light. You are standing in between the pillars of a ancient stone gate way. You have no idea how you got here, and you realize you don't remeber anything about yourself. A wild bearded man in tattered robes approaches loudly exclaiming. "Ah the gods have sent more to us, Welcome, Welcome strangers to our lands". "You will have many questions , yes but first you should eat and drink to regain some of your vigor". He and several others all similarly dressed drag you down the hill top to a small town and into a tavern. As you eat a hearty meal and drink some good wine or ale some small bit of memory returns.
At this point the characters can remember their names and classes/levels (if applicable) but that's it. No other details, as they are just created characters their aren't any of course.
As you eat the bearded man explains; you have been sent to us from other places and we can help you start your new life here with us. " You are welcome to settle here if you wish, some newcomers have of course, but you may wish to continue your chosen professions as well".
The next few days are spent teaching you of the lands and customs that they know of. This is of course the sketch notes of the world they will be adventuring in. Any gaps in knowledge can be attributed to lack of recall or something that was not known to the villagers of the gateway. I thought of this with D&D in mind but will work for any RPG. This was designed after seeing a number of adventuring groups fail to understand the world they were in. This offers an easy explanation for this lack of knowledge.