How do substitution and addition reactions differ?
A substitution reaction is when you replace a single functional group with another. An addition reaction is when you add a functional group to a compound.
Common examples of substitution reactions are SN1 and SN2 reactions, where the nucleophile attacks the electrophile to replace a functional group. There are two types of polar addition reactions: electrophilic addition reactions and nucleophilic addition reactions. The non-polar additions are free-radical addition reactions and cycloadditions. Hope this helps.