What are SN1 and SN2 reactions?
SN2 and SN1 reactions are types of nucleophilic substitution reaction that often involve substitution of one nucleophile (such as OH) by another nucleophile.
SN2 (substitution, nucleophilic, bimolecular) takes place in a single step without intermediates when a nucleophile reacts with the substrate(e.g. alkyl halide) from a direction opposite opposite to the leaving group.
SN1 (substitution, nucleophilic, unimolecular) is a first-order step, where the concentration of the nucleophile does not affect/appear in the rate-limiting step.