From "Law, Sex & Christian Society in Medieval Europe" by James Brundage:
Early Germanic law recognized three legitimate methods of contracting marriage: by capture (Raubehe), by purchase (Kaufehe), and by mutual consent (Friedelehe). Bride purchase involved an agreement between two families. An exchange of property was an essential part of Kaufehe and the Germanic law codes encouraged this type of marriage. Most of the codes envisioned a threestage process of contracting Kaufehe. It began with an agreement (Muntvertrag) between the suitor or his father and the father or guardian of the prospective bride, concerning the compensation to be paid to the woman's family by the groom's family. This stage of the process corresponded more or less to desponsatio in Roman law. Muntvertrag was followed by a public transfer (Anvertrauung) of the bride to the head of the groom's family. This was followed by a wedding ritual (Trauung), during which the members of the bride's clan stood in a circle around her to witness the transfer and to signify their consent to the transaction. The process involved conveyance not only of the person of the bride to the family of the groom, but also of legal power (Munt, mundium) over her to the husband and his family group.9 The bride's ties with her family of origin were, in effect, severed, and she was integrated into her husband's family. This type of union, involving active participation and control by the families of the parties, was the preferred type of marriage.
Marriage by capture or abduction (Raubehe) was accomplished by forcible abduction and ravishment without the consent of the woman or her family; it is therefore sometimes referred to as marriage by rape. The law codes discouraged such marriages, and some of them imposed heavy fines on men who forcibly married free women. A man who did not wish to risk the legal and physical hazards of marriage by abduction and who was either too poor, too powerless, or too mean to purchase a bride had the alternative of marrying by consent. Friedelehe may in fact have been an outgrowth of Raubehe. The term Friedelehe designated marriage by elopement, to which the bride consented, but her family did not. It was distinguished from Kaufehe by the lack of a betrothal or dowry agreement and by the fact that the husband did not acquire Munt over his wife. In Friedelehe the woman's Munt remained with her family: she continued in effect to be a member of her family of birth, even though she lived with a man who belonged to another family.