春卷 (Chūnjuǎn, Spring rolls) are julienned vegetables, sometimes with a bit of noodles, sometimes with a bit of minced meat, wrapped with a flour dough skin and pan- or deep-fried.
They are a filled roll.
You can see the different varieties by country here:
http://en.wikipedia.org/wiki/Spring_roll Spring roll: 鸡蛋卷 (Jīdàn juǎn, Egg rolls) are many different things around the world.
In Chinese communities, these typically refer to a sweet biscuit type roll, of hollow flaky egg pastry (not filled.)
However, there is also another variety (common in American Chinese cuisine) where a flour dough wrap is filled with "pork, shrimp, or chicken, adding cabbage, carrots, bean sprouts and other vegetables, and then deep fried."
In the American Chinese respect, I believe it is very similar to a Spring roll really, although the flour dough looks thicker and of a different composition than a typical Spring roll (the dough bubbles when deep-fried, with Spring roll skin it does not.)
http://en.wikipedia.org/wiki/Egg_roll Sweet egg roll: American Chinese egg roll:
cooking.stackexchange.com/users/24248/Ming
If you're talking about American-"Chinese" cuisine, there may be a different distinction: Vietnamese spring rolls are always wrapped in rice paper, and are commonly sold as just plain "Spring Rolls", whereas "Egg Roll" is more common for the Chinese-style roll made with an egg-based batter (pictured in setek's answer).
While it would not be wrong to call an egg-batter-based roll a "spring roll" per se, it would definitely be wrong to call these types of rolls "egg rolls" since they do not contain eggs.
These rolls also tend to be made vegetarian or with shrimp only, rather than having pork or chicken.
Vietnamese Gỏi cuốn ("Spring roll"): Vietnamese Nem rán ("Fried Spring Roll") (Note that this uses the same kind of wrapper as the above, but fried):
cooking.stackexchange.com/users/6317/Yamikuronue
Well, with regards to this post, the comments all note different things.
Being from a chinese/vietnamese family with traditional recipes passed through the generations, let me just say this:
Eggroll (savoury): has egg in the filling.
In vietname culture, may be consume wrapped in lettuce and dipped in fish sauce.
In chinese culture, these badboys are generally eaten as is.
Eggroll (sweet): mentioned in a previous post.
No filling, jsut a roll that is sweet.
Springroll: no egg in the filling, may be vegetarian.
Fresh roll: rice paper filled with vermicelli rice noodles, lettuce and some sort of meat, porkskin and/or shrimp.
A vietnamese style culinary roll often eaten with hoisin sauce
cooking.stackexchange.com/users/34619/user34619
Chinese Egg Roll (US) - Similar to Chinese Spring Roll
A wheat flour roll, deep fried with or without batter.
Egg Roll - Simlar to Krum Kake, Wafer, Pizelle, Bricelet A
(usually sweet) waffle based batter that is usually wrapped into a cylinder.
Vietnamese Summer Roll
A rice paper roll that is filled and usually served cold.
Vietnamese Spring Roll
A rice paper roll, that is deep fried.
Heaven knows why anyone described a Chinese spring roll as an egg roll, but then again "Pants" definition in US versus UK English...
cooking.stackexchange.com/users/47760/Food Lover
There's lots of different types of things that are called spring rolls in Asian cuisine.
these can be fried or not fried, usually with some sort of rice flour based wrapper.
Typically, egg rolls are always fried, larger and made with a wheat flour wrapper.
cooking.stackexchange.com/users/17461/pauljc
Many of my friends ask how they should refer to Vietnamese egg rolls and spring rolls, and how to differentiate between these two.
As I read these comments and am confused by the various interpretations.
In my Vietnamese family Goi Cuon is a Spring roll, the transparent rice wrap with shrimp, noodles, and so on.
Cha Goi is a traditional Viet egg roll.
Yes, you can fry a Spring roll but the name would be different: from my perspective, Goi Cuon is the cold roll and Cha goi is the fried roll.
They have different fillings and sauces, that's all.
And don't ask a Viet person about summer rolls; I had never heard this term until foreigners asked me about it; this term doesn't exist for me.
cooking.stackexchange.com/users/52478/Tami
The final challenge for a recent "Master Chef" was to make spring rolls. It seemed to me that they were really making egg rolls, like I've seen at any restaurant I've ever been to -- Chinese, Vietnamese, Thai, etc.  What is the difference between a spring roll and an egg roll?
What is the difference between a spring roll and an egg roll?
cooking.stackexchange.com
<asian-cuisine>
cooking.stackexchange.com/questions/45427
cooking.stackexchange.com/users/4267/xenoterracide
There are several kinds of Spring roll in Chinese, Vietnamese and other Southeast Asian cuisine, as well as American varieties, but generally they include julienned vegetables, sometimes with meat, chicken or fish, wrapped in a flour dough or rice wrap and pan- or stir-fried. Egg rolls are similar, but often larger and with egg in the filling. Spring rolls contain vegetables and maybe pork or shrimp. In the Vietnamese tradition they are wrapped in a rice wrap. Egg rolls, on the other hand, are wrapped in a wheat wrap and contain egg. There is some confusion in the names used in Chinese/Vietnamese cuisine and Chinese American cuisine.
Spring rolls contain vegetables and no egg. They may contain shrimp or meat. In Vietnamese cuisine they are made with a rice wrap. There are differences between Chinese cuisine and Chinese American cuisine. In Vietnamese cuisine, egg rolls have egg in the filling. They are typically larger and fried and have a wheat wrap.