from When a Jew Celebrates

In the Bible and the Talmud there were two separate ceremonies Connected with marriage. There was the ceremony of betrothal and the actual marriage. The two ceremonies could be a year apart. In Betrothal the couple were legally bound together although the bride lived in her father's house. They couldn't change their mind's. They would have to get a divorce.
The custom began during a time when the bride was bought. At the betrothal, the price was agreed upon and a contract signed. The money was necessary because every member of the family worked, including the young girl. When she got married she went to her father-in-law's house and helped there. So, in away, the father-in-law paid the father for the loss of the daughter's services.
But even in those days, if the bride's father was well-to-do, he gave the bride's price he received to his daughter as a present. Even the Poor father's probably gave back part of the money.

To the betrothal ceremony came entire families of both the bride and the groom and it ended with dancing and feasting and merry making.
Months later, the groom came to take his bride to his father's house. At the time the bride's price was actually paid-and again there was a great family feast and celebration. But most important of the ceremonies were the betrothal and contract signing.

In the first century C.E. the Sanhedrin changed the marriage contract. In the new contract, the groom only promised to a certain amount for the bride. Ne didn't actually pay the money. Instead, he gave the bride a perutah, the smallest coin at the time as the token of the brides price. The rest of the money had to be paid only if the couple got a divorce.