This is a VERY short blog: I am just amazed how many people seem to not know that a cold and the flu are all viral conditions! EVEN SCIENTISTS! So just to clarify. There are at least (hedging my bets) three types of infection you can get: (1) Bacterial, (2) viral and (3) parasitic.
A "cold" is a virus.
The "flu" is a virus.
"A virus" is a virus (people often say, "I don't have a cold/the flu I have a virus"!!).
Typically, but not exclusively food poisoning will be bacterial. (And parasites include tapeworms and fleas.)
The distinction between a virus and bacteria is pretty crucial: Antibiotics are anti-bacterial, but have no effect on viruses. Sometimes, a bad cold, with all the sneezing and wheezing and lying around indoors can leave with you with a secondary bacterial infection, but wasn't the primary cause! In terms of how viruses and bacteria are different... well just log on to Wikipedia!