Simple Definition:

Pantheism is the belief that the entire universe or nature is divine and should be respected and revered. [Divine means having a spiritual or god-like quality.] For example, pantheists view the sun, trees, and animals as sacred and deserving of worship or admiration.

Very Simple Definition:

Pantheism is the belief that everything in nature is sacred and should be respected. For example, pantheists consider the sun, trees, and animals as special and worthy of care.