What do Genesis chapter 38 verses 1-10 mean?

Answer 1

Genesis 38:1-10 says that Jacob had three sons, Er, Onan and Shelah.

Genesis says that Er was evil, so God killed him. Judah told Onan to take Er's wife, Tamar, as his own, as was common practice among the early Hebrews. Onan did so reluctanty and, when having sexual intercourse with her, was careful to wihdraw so as to spill his semen and avoid a pregnancy. Although this was not evil, it nevertheless displeased God, who also killed Onan.

Later, Tamar disguised herself as a temple prostitute (commonly translated as 'harlot', but the Hebrew word for a common prostitute is quite different), so that she could have intercourse with Judah, her father-in-law, and bear his child.

For more information, please see:

http://christianity.answers.com/bible/the-book-of-genesis
http://christianity.answers.com/theology/the-hebrew-patriarchs-in-history-and-tradition