The difference between grounds for nullity and grounds for annulment is that grounds for nullity apply to particularly serious defects in which the marriage is dissolved retroactively (ex tunc). Nullity exists, among others, in the case of a lack of marital capacity, a double marriage, or kinship.
An annulment can only be requested by one of the two spouses if certain defects of will exist. In this case, however, the marriage is dissolved only for the future (ex nunc). In practice, however, annulment plays a minor role. Examples are, for example, the mistake that it is a marriage or the mistake about the identity of the spouse.
