What is meant by floral formula ? Which signs are used to make floral formula ?

$\rightarrow$ Various morphological features are used to describe a flowering plant. The plant is described beginning with its habit, vegetative characters - roots, stem and leaves and then floral characters inflorescence and flower parts.
$\rightarrow$ After describing various parts of plant, a floral diagram and a floral formula are presented.
$\rightarrow$ The floral formula is represented by some symbols.
$\rightarrow$ The floral formula and floral diagram shown in figure represent the flower of mustard plant.$\rightarrow$ In structure of floral formula, after the number of specific whorls, the number of constituent elements of that whorl is presented. The number of units of its floral whorls keep changing according to flowers.