According to thefood dictionary at Epicurious.com ... an egg
roll is a small, stuffed Chinese pastry usually served as an
appetizer, filled with minced vegetables and meat, rolled in a
wrapper which is make of egg, salt, water, and dough, then deep
fried.
A spring roll is smaller, more delicate version of an egg roll
and are traditionally served on the first day of the Chinese new
year... which takes place in early spring. Even though the recipe
to make egg roll and spring roll are the same, typically egg roll
wrappers are a little thicker.