Nutrient agar is a microbiological growth medium

Growth medium

A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....

 commonly used for the routine cultivation of non-fastidious bacteria. It is useful because it remains solid even at relatively high temperatures. Also, bacteria grown in nutrient agar grows on the surface, and is clearly visible as small colonies. In nutrient broth, the bacteria grows in the liquid, and is seen as a soupy substance, not as clearly distinguishable clumps.
Nutrient agar typically contains (w/v

Percentage solution

"Percentage solution" is an ambiguous term which is used to describe a solution with the unit "%". It may refer to:* Mass fraction if mass/mass is meant...

):

• 0.5 % Peptone
• 0.3 % beef extract/yeast extract
• 1.5 % agar
  Agar
  Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
  
  
• 0.5% NaCl

distilled water

• pH adjusted to neutral (6.8) at 25 °C.

Nutrient broth is made identically, except omitting the agar.