Direct Sun: These plants are happy out in the sun all day. Rooms facing East will get direct morning sun and rooms facing West will get direct afternoon sun. Afternoon sun can scorch most houseplants so beware!
Indirect Light: This is light that bounces off another surface before reaching your plant. North facing windows usually receive bright indirect light, and rooms with south facing windows usually receive medium indirect light. Plants that prefer indirect light are happy with some level of direct morning sun also.
Filtered Light: This refers to light being blocked by objects such as curtains or other plants. Most plants that prefer filtered light grow in the understory of forests where they receive dappled light through the canopy of other trees.
Low Light: Most plants need some access to natural light. Some plants will survive in lower light conditions with less access to natural light sources and some can survive entirely on artificial fluoro light such as in an office without windows. Low light plants may tolerate low light conditions but will more likely thrive and grow in brighter conditions.