Form

The form is the couple’s inward consent or agreement to become husband and wife which is outwardly expressed by the matter.

After the ring(s) has/have been given and received, the priest speaks to the people.  You will notice that mention is made of the ministers of the Sacrament (the bride and bridegroom), the form (the consent of the couple), and the matter (the vows and signs):

“In the presence of God, and before this congregation,
(John) and (Mary) have given their consent
and made their marriage vows to each other. 
They have declared their marriage by the joining of hands
and by the giving and receiving of rings. 
I therefore proclaim that they are husband and wife”. (2)

The priest then joins their right hands together and says:

“Those whom God has joined together let no one put asunder”. (3)