How do B&Bs work?

Could you possibly elaborate on how bed and breakfasts operate? I'm quite curious about the inner workings of these establishments. Do guests typically book in advance, or are walk-ins welcome? What kind of amenities are typically included? Are breakfasts included in the room rate, or is it an additional charge? Also, how does the check-in and check-out process work? I'm interested in understanding the overall guest experience at a B&B. Thank you for your time and explanation!