So, like do you mean... before the session starts (for example to get a feel if they're into it or not)? or do you mean like, with the session underway?

Before the session starts, I generally just descibe the setting and vibe the campaign has. If it's another person's campaign (precanned from the source books or someone else's,) I'll tell them where it comes from.

if we have a new player, I'll go into more detail there; specifically as part of the session zero with them; so that I'm getting a feel for what they like and if I need to change it up or add to it so they get something out of it.

Once the session begins, I'll open up in a social setting- a bar, tavern or inn, maybe something like a temple hostel; where we can place the characters and let them meet each other. (especially if it's the first time the characters are meeting.) this gives the players an opportunity to establish basic personality etc; while also letting me start getting into the worldbuilding.

I generally don't do too much in the way of details on where things are located. I do have detailed encounters that i drop as they move about instead, "you come on a broken down wagon" type thing. (or a corpse. or just a little girl asking for help.)

this way you build out the map as you go; and you just focus on giving them an immersive world to explore and be little shits in. you want to nudge them, not shove them, and let them set the tone and passing. Sometimes, they just want to get drunk in a tavern, after all.

Build the world around the narrative unfolding, rather than trying to get them into some super detailed GRR Martin-esque world that they're then just gonna go sit in a pub picking fights with the gnomes while the bard tries to bang everything in sight. You don't have to make everything up on the fly, but don't worry about a city they may never reach. have taverns and inns and farmyards and bridges ready to go, They don't have to be totally unique, even. Have a list of names- people, streets, whatever- to drop as you need to. Precanned enough so that you can keep it fluid without sacrificing flexibility. (boss rooms, though, do require attention to detail, lol. or just things I want them to think is the boss room...)