The common cold is caused by a virus which infects the nose.  Contaminated droplets are breathed in through the nose or brought to the nose by hands. The virus is carried to a place at the back of the nasal passages called the adenoid area.  The sinuses, ears and bronchial tubes can also be affected by a cold virus.  There are over 100 different viruses that cause cold symptoms.  The most common of those viruses is the Rhinovirus.

The flu is caused by a completely different virus than a cold: the influenza virus.   When you catch the flu the symptoms are all similar to those of a cold, but with a few variations and usually lasting much longer.  Unlike a cold, the flu can be dangerous for young children, people with weakened immune systems, and the elderly.

A cold usually lasts somewhere around a week.  It takes 8-12 hours from the time you contract the cold virus to the time when you start to exhibit the symptoms and can pass it along to someone else.   The symptoms that you feel are different ways your body is responding to, and trying to fight away the virus.

The flu can last a lot longer than a cold, sometimes two or more weeks.  It also comes with some more severe symptoms like muscle aches and fever.