Difference between SN2 Reaction and Electrophilic Addition

[Sebastian Hurtado 1J]

What is the difference between a bimolecular nucleophilic substitution reaction (SN2) and an electrophilic addition reaction? I know the former involves the addition of an electrophile while the latter involve the substitution of a nucleophile, but when given a chemical reaction formula, how would you determine which type of reaction it is? Are there specific differences between the two, e.g. number of steps?

[Caroline Chen 2A]

For an addition reaction, you take two things and make one. For a substitution reaction, you take two things and end with two things.