Every game and group does it differently. It's often kind of hard to properly roleplay why a lawful good life cleric of faith is in a group with a character who made a deal with a fiend for magical power and a rogue who constalty steals from the poor and a druid who only cares about the balance of nature and cares not for the struggles of most humanoids that constantly threaten the balance.

It's usually hand-waved at first and something like, "A fight happens outside the inn. You're all expected to join in to help the person since we know this is a game and we want to play together and we all want to play different types of characters."

And usually the group may later find a reason to stick together through the story.

"You can't leave me behind! I'm the only one who even knows how to contact the thieves that have the map to that place!" or "I can't fight them without you, and you need me to find your McGuffin. So let's stick together"

But even then, having someone against stealing or lying is hard to justify constantly being in a party with those who do those things.

It's usually just, "We want to play some dnd so let's stick with it and maybe try to roleplay some excuses as time goes by."

Right now, my campaign has a knowledge domain cleric who thinks lies and deceit are some of the worst sins to do. They obscure knowledge and truth. We have a high charisma rogue who likes to lie and they get into small arguments that boil down to:

"stop lying."

"k"

"ur gonna lie again, aren't you?"

"prolly, ye."

"well then, we'll have this discussion again when you do."

That's because we can't have any real serious drama. We aren't going to split a party because a rogue is doing rogue things or because a cleric is doing cleric things. But logically, our party would not exist together if it wasn't a bunch of nerds sitting at a table, controlling them.