Nucleophilic Substitution:
Definition
The existence of a strongly electrophilic carbon center creates alkyl halides susceptible to nucleophilic attack whereby a nucleophile displaces the halogen like a nucleophilic halide ion. The reaction is termed as nucleophilic substitution and there are two kinds of mechanism - the SN1 and SN2 mechanisms. Carboxylic acids and carboxylic acid derivatives also go through nucleophilic substitutions, but the mechanisms are completely different.
Figure: Nucleophilic substitution.