Bacteria(monera) consist of organisms with prokaryotics cells. There are 3 majors domains ; bacteria,eukaryota and archaea.

Characteristics of bacteria
Bacteria can be define as 

• Small size
• Ability to reproduce rapidly
• Most abundant and diversified organisms 
• Diversity of habitats and modes of existence
  

  
Shapes
Most bacteria comes into one of these 3 shapes :
Rod shaped= Bacillus 

Spherical=Coccus

Spiral=Spirillum

Some bacteria organized into groups :
Diplo= Pair= Diplococci

Strepto= Chains= Streptococci

Staphylo= Cluster= Staphylococci