In Vietnamese cuisine, a spring roll consists of lettuce, mint, noodles, and either pork or shrimp wrapped in rice paper and eaten with either a fish sauce (nuoc mam) mixture or a peanut sauce made of peanut butter, hot sauce, hoison sauce, and crushed peanuts. An egg roll has grounded pork and shrimp along with various small herbs and carrots wrapped in the egg noodle dough and deep fried. They're not always wrapped in egg noodle dough, sometimes they're wrapped in rice paper. Egg rolls are about half the size of spring rolls.
Egg rolls originated in China, while Spring Rolls are a Vietnamese dish, although the Vietnamese have they're own versions of egg rolls and the Chinese have they're own versions of spring rolls. Egg rolls can have meat or vegetarian, and same applies for spring rolls.
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I am Vietnamese. I just know this stuff.