Do yellow leaves indicate over-watering?

Yellow leaves are a  common symptom. There are multiple causes including too little water, inadequate light, excess fertilizer, insects, too much light, disease or chlorides in the water.

Do interior plants need to be in the window?

Only some indoor plants benefit from direct sun. Often, plants acclimate to different light intensities. A ficus leaf will thicken and actually grow to a smaller size in full sun. But when your plant is happy, don't move it.  Indoor plants are often acclimated to the shade. These plants might suffer when exposed to direct sun.

Do plants need nutrients to make them grow?

Houseplants in a controlled production greenhouse are kept in an ideal conditions for rapid growth. Some plants and production flowers are even hybridized for fast growth characteristics.

Nutritional needs of a plant in a production green house are greater than in a typical personal house plant environment where humidity, light, irrigation, and air circulation are not ideal. After being removed from the production greenhouse the plant slows evapotranspiration. Likewise after being brought into a typical household the watering and nutitional requirments decline, the plants growth rate declines and the nutritional needs decline. Plants use most of the carbon that they release from Co2 to create energy but some of the carbon feeds plant growth. Far less plant food comes from the soil.

Do plants need a big container to get big?

The fastest growing plants are those that are moderately potbound. Frequently repotted plants put much of their energy into growing more roots, at the expense of leaves and flowers. Plants in large pots are also much more likely to suffer from root rot..

Do indoor plants only grow indoors?

There's really no such thing as an "indoor" plant in nature. They're all exterior plants. But most are shade loving and temperature sensitive because they are typically from tropical zones.