What is decarboxylation?

Hint:As the name suggests, the decarboxylation is related to the removal of the carboxyl of the carboxyl group releasing the carbon dioxide. Generally, this is the reaction of carboxylic acids removing carbon atoms atoms from the chain.

Complete step-by-step answer:Let us know more about the decarboxylation;
Decarboxylation-
It is a chemical reaction that removes a carboxyl group as we have known this earlier forming carbon dioxide. The enzymes enzymes (biological catalysts) which cause this mechanism are the decarboxylases or carboxyl-lyases.
This can be formally be shown by a reaction as follows;
$R-COOH\to R-H+C{{O}_{2}}$
The day-to-day chemistry has the simplest example of decarboxylation i.e. respiration i.e. oxidative breakdown of glucose to form water, carbon dioxide and ample amount of energy.
More specifically, in organic chemistry the term decarboxylation represents the replacement of the carboxyl of the carboxyl group with hydrogen atom; which can be clearly seen in the above reaction. There are 4 types of decarboxylation i.e. Barton decarboxylation, Kolbe electrolysis, Kochi reaction and Hunsdiecker reaction (named decarboxylation reaction).

Note:Do note that the reverse process of decarboxylation i.e. carboxylation is the first step in the process of photosynthesis photosynthesis occurring in plants which is simply the addition of carbon dioxide $\left( C{{O}_{2}} \right)$ .