Hi there,
I'm vegan and I've just signed up to clarify this matter.
Vegans do not use the products of animals in any way, shape or form. So we don't eat meat, poultry, fish, as these have to be killed directly to be eaten.
We also don't eat dairy and eggs, as although the animals aren't killed directly, there is still just as much suffering in these industries as the meat industry. Male hatchlings are sorted by conveyor belt in their 1000s, and either end up in the compacting machine to be ground up alive or asphixiated. So for every female laying hen one male chick suffered this fate. Also, when females' egg laying capacity declines, they are sent off to slaughter for cheap meat products.
Likewise with the dairy industry, for every female milking cow, a male calf was born whose usual fate is to be separated from its mum at a day old and sent to be raised for veal. This causes extreme anguish and distress for both. So there is no effective difference morally between milk and veal. Females are also forcibly impregnated by the farmer's hand and kept in a constant cycle of pregancy, birth and lactation before being sent off to the knackers long before her natural life expectancy.
Eggs and milk and other by products are still part of the slaughter equation, and as vegans we try to remove our selves from it as much as possible and practical. Modern life does make it difficult to avoid entirely, eg matches and car tyres, but just because we can't be perfect, it's no excuse for not doing anything.
As for leather, vegans do not use leather; it doesn't matter that the cows were raised directly for their hides, or if it's a by product from the meat industry, we still reject any use of animals for human ends.
For wool, the same applies, it's still wrong to expropriate any animal parts or bodily secretions, no matter if you don't have to kill the animal to get them, it's a violation of their integrity to keep them in captivity and take a life for mere human whim.
Some vegans will still continue to wear leather and wool if they bought it before going vegan, and gradually replace these items as circumstances and finances allow.
As for fossil fuels, there is no direct animal rights issue here as the animals in question have long since been dead. However, many vegans are very ecologically minded as we see the connection between fossil fuel emissions and habitat destruction for wild animals... So we try to live as lightly as possible, and being vegan is also enormously beneficial in this regard too. Also, using public transport, minimising flights, cutting down on packaging, not buying so much consumerist 'stuff' etc etc.
Addressing the issue of collateral damage of small animals in harvesting machines in soya/ wheat etc production, most of these arable crops are grown for animal feeds. As the conversion efficiency of plant protein to animal protein is only something like 1:4 to 1:10, it causes much less suffering an death to these small creatures by eating the plants directly, than eating them 'secondhand' in the form of animal flesh
So to sum up...
If the animal has to be killed directly to get the product = neither vegetarian nor vegan
If the animal doesn't have to be killed first = vegetarian, but not vegan
Only if a product is completely animal product free it is considered vegan.
Hope that helps to clarify any misconceptions about veganism.