Swine flu is a form of influenza that originated in pigs but can be caught by, and spread among, people.
Swine flu is a respiratory disease of pigs caused by type A influenza viruses. Outbreaks of swine flu happen regularly in pigs. People do not normally get swine influenza, though infections do sometimes happen. In the recent past, most human cases of swine influenza have been in people who were in close contact with pigs, such as farmers. In the current outbreak,

The symptoms of swine flu are broadly the same as those of ordinary flu, but may be more severe and cause more serious complications.

The typical symptoms are:
sudden fever, and
sudden cough.
Other symptoms may include:
headache,
tiredness,
chills,
aching muscles,
limb or joint pain,
diarrhoea or stomach upset,
sore throat,
runny nose,
sneezing, and
loss of appetite.
If the flu becomes pandemic, potentially, everyone is at risk because few people, if any at all, will have immunity (resistance)

Preventing the spread of germs is the single most effective way to slow the spread of diseases like swine flu.
You can protect yourself and your family by:
ensuring everyone washes their hands regularly with soap and water, and
cleaning surfaces regularly.
You can prevent a virus spreading to others by:
always carrying tissues,
using tissues to cover your mouth and nose when you cough and sneeze,
binning the tissues as soon as possible, and
washing your hands regularly.
CATCH IT. BIN IT. KILL IT

the virus has been spread by person-to-person contact.
In the current swine flu outbreak, human infection with swine influenza A (H1N1) viruses have also been confirmed in the US, Canada, Spain, the UK, New Zealand, Israel and Germany.
This has given rise to concern that the outbreak could become a pandemic flu - a global outbreak of flu that spreads quickly because it is a new type of virus that few, if any, people have resistance to.