the adverb 'indoors' refers to the inside of a building or home. Indoors is used to describe a place that is surrounded by walls and has a roof overhead. It is commonly used to distinguish between activities that happen inside something such as a house and activities that happen outside. Indoors can also be used to describe the interior of a vehicle or another form of transportation.
1. I love playing indoors when it's raining outside.
2. We'll have to take the conversation indoors to keep us out of the rain.
3. I prefer driving a car indoors rather than using public transportation.
indoors usually comes after the verb and is not found in the subject of a sentence.