The building in question is the Celadon City Mansion, which is only accessible in Pokemon Red and Blue. It's the home of the Team Rocket goons, and they've done a lot of damage to it by starting a fire.
Here's what you can do in Celadon City in Pokemon Yellow:
* Visit the Department Store: This is a great place to shop for items, including clothes, furniture, and even a rare item called the Silph Scope, which is crucial for getting into the Silph Co. building.
* Challenge the Gym Leader: Erika, the Grass-type Gym Leader, awaits in the Gym at the top of the department store. Be sure to bring strong Fire or Flying-type Pokemon!
* Explore the Game Corner: This building is full of slot machines and other gambling games. You can win prizes, including rare Pokemon.
* Visit the Game Corner: This is a fun place to play games and earn prizes, but be careful not to get addicted!
* Find the Missing Trainer: You can help a trainer who lost their Pokemon in the park.
* Explore the surrounding area: There are lots of other things to discover around Celadon City, including trainers to battle and wild Pokemon to catch.
While you can't go inside the burnt building in Pokemon Yellow, there are still plenty of things to do in Celadon City!