There are different types of vows. A few had taken a vow of a Nazirite and some had made vows not to touch wine or special foods. Likewise different people may make different types of vows. When Christians receive baptism, they make a promise of vow that they shall leave sin and seek holiness. Some others offer themselves to God for doing His ministry.
Some people make vows of money or property.
Whatever be the nature of vow made in the above manner, it should be fulfilled. Not making a vow is not as sin. However those who make vows should fulfill them at any cost. If you make a vow to the Lord your God, do not be slow to pay it, for the Lord your God will certainly demand it of you and you will be guilty of sin. But if you refrain from making a vow, you will not be guilty of sin.