"Rainbow Bridge" is a poem about where a pet goes after it dies. The rainbow bridge in the poem is similar to "Bifrost," a burning rainbow bridge connecting this world to the afterlife in Norse mythology.
According to the poem, the rainbow bridge is a bridge "just this side of heaven" where animals cross over from this life to the next. Once a pet dies and crosses the rainbow bridge, it feels no pain or sadness. It lives in a meadow, where it has plenty of food, water and space to run around and play in the sunshine. Old pets have energy, and sick pets are well again. Yet, no matter how happy the pet is, it continues looking for its owner every day. When it is the owner's time to pass on, he and his lost pet reunite, and both experience tremendous joy. Then they cross the rainbow bridge together into Heaven.
It is unclear who wrote the original "Rainbow Bridge" poem. Some possible authors include Paul C. Dahm, who published a book of the same name in 1998; William N. Britton, who wrote "The Legend of the Rainbow Bridge," published in 1994; and Dr. Wallace Sife, author of the poem "All Pets Go to Heaven," and the book "The Loss of a Pet."