Why do snails leave a slime trail?

Snails leave a slime trail because of their limited movement. Snails are very small creatures, and coupled with the wait of their shell, they do not move very fast. Snails leave a trail of mucus, not slime (well i guess it counts as slime..:) in order to help them slip along faster. They use it to glide along on, and it helps them stick so they can hang upside down.