The Book of Ruth gives the link in the genealogy of King David and of Christ who is called "the son of David" (Matthew 1:1-16, Romans 1:3, II Timothy 2:8).
Ruth was a Gentile and married an Hebrew husband.
The Book of Ruth also shows the type (pattern) of the coming Christ who
would be the kinsman redeemer to God's people.
Ruth 1:14-18:
Ruth decided not to leave her mother-in-law - even though Ruth's husband (Naomi's son) had died. She told Naomi that the Judean people will be her people and that Naomi's God (the only true God) will be her God. Ruth refused to go back to her own family and the gods which they worshipped and served even though she may have found a new husband there, plus Naomi had given her the freedom of doing so.
Ruth chose the only true God as her God and to do
what He would want her to do, instead of what her natural family with
their false gods would have wanted her to do.
Ruth 2:1-3:
God is letting the reader know that Naomi had a
relative (kinsman) of her husband. Usually, when a woman's husband died,
it was up to her husband's brother to marry her in his place and so keep
the man's seed alive via any sons born to him (if there was no brother,
then the next nearest relative, and so-on down the line of relatives).
Ruth 2:8-16:
Boaz came to know who Ruth was. He arranged with her, and the young men also working there, that she could work freely without harassment and glean the food that she required for herself and Naomi. (Note that Boaz did not just give her a "handout" - he made sure that there would be plenty there waiting for her but she would have to work in order to receive it!)
Ruth behaved herself and did her best for her mother-in-law, and she worked honestly to get food for both of them.
Ruth 2:20:
Naomi tells Ruth who Boaz is.
Ruth 3:1-5:
Naomi tells Ruth what to do in order for them to be redeemed from their situation, and Ruth did not object but agreed to do all she was told to do.
Ruth 3:6-13:
Ruth carried out the instructions precisely, and told Boaz exactly what Naomi told her to say, and Boaz recognized that she was telling the truth. However, Boaz knew that there was a closer relative than he was and so that closer relative had the right to redeem Naomi and Ruth, and he could marry Ruth if he so desired to. Boaz also did what was correct and did not wrongfully take advantage of Ruth's situation.
Ruth
When Naomi asked Ruth how she got on, Ruth told here
everything - there were no secrets between them.
Ruth chapter 4:
Boaz legally redeemed Naomi and Ruth, taking Ruth as his wife.
Ruth had a son named Obed, the father of Jesse, the
father of David who became the king and prophet of God (refer to Matthew
1:5 and 6).