Lobar pneumonia affects a section (lobe) of a lung. Bronchial pneumonia (or bronchopneumonia) affects patches throughout both lungs.

Lobar Pneumonia	Bronchial Pneumonia

Causes of pneumonia:
1) Bacterial
Bacterial pneumonia can attack anyone from infants through the very old.  The most common cause of bacterial pneumonia in adults is a bacterium called Streptococcus pneumoniae or Pneumococcus.
Pneumococcal pneumonia occurs only in the lobar form. When a person's resistance is lowered, bacteria invade the lungs and inflame the air sacs. The tissue of part of a lobe of the lung, an entire lobe, or even most of all the five lobes, becomes completely filled with liquid matter. The infection quickly spreads through the bloodstream and the bacteria infects the whole body. It is the only form of pneumonia for which a vaccine is available. 

2) Viral
More and more viruses are being identified as the cause of respiratory infection: 
Half of all pneumonias are believed to be of viral origin.  Most viruses attack the upper respiratory tract but some produce pneumonia, especially in children 
Most viral pneumonias are patchy and self-limiting 
Primary influenza virus pneumonia is severe and may be fatal:
The virus invades the lungs and multiplies 
There are almost no physical signs of lung tissue becoming filled with fluid 
Pregnant women or people with pre-existing heart or pulmonary illness are most susceptible 

3) Mycoplasma
Because the symptoms and physical signs of mycoplasma pneumonia, along with the course of the illness, differ strikingly from those of classic pneumococcal pneumonia, mycoplasma pneumonia was once believed to be caused by one or more undiscovered viruses, and was called "primary atypical pneumonia." 

Identified during World War II, mycoplasmas:
are the smallest free-living agents of disease in humans 
are unclassified as to whether bacteria or viruses 
possess characteristics of both bacteria and viruses 

The pneumonia caused by mycoplasmas:
is usually mild and widespread 
affects all age groups 
occurs most frequently in older children and young adults 
rarely causes death, even in untreated cases 


4)Other
Many of the less common pneumonias have a high death toll and are occurring more often. Various special pneumonias are caused by the inhalation of: 
food 
liquid 
gases 
dust 
a foreign body 

Pneumonia can also be caused by a bronchial obstruction such as a tumour.

Rickettsiae cause Rocky Mountain spotted fever, Q fever, typhus, and psittacosis --diseases that involve the lungs to a greater or lesser extent. Tuberculous pneumonia is an overwhelming lung infection and extremely dangerous unless treated early.