These are rules to live by. They are somewhat analogous to the second half of the Ten Commandments in Judaism and Christianity -- that part of the Decalogue which describes behaviors to avoid. However, they are recommendations, not commandments. Believers are expected to use their own intelligence in deciding exactly how to apply these rules.
1.Do not kill. This is sometimes translated as "not harming" or an absence of violence.
2.Do not steal. This is generally interpreted as including the avoidance of fraud and economic exploitation.
3.Do not lie. This is sometimes interpreted as including name calling, gossip, etc.
4.Do not misuse sex. For monks and nuns, this means any departure from complete celibacy. For the laity, adultery is forbidden, along with any sexual harassment or exploitation, including that within marriage. The Buddha did not discuss consensual premarital sex within a committed relationship; Thus, Buddhist traditions differ on this. Most Buddhists, probably influenced by their local cultures, condemn same-sex sexual activity regardless of the nature of the relationship between the people involved.
5.Do not consume alcohol or other drugs. The main concern here is that intoxicants cloud the mind. Some have included as a drug other methods of divorcing ourselves from reality -- e.g. movies, television, the Internet. 1
Those preparing for monastic life or who are not within a family are expected to avoid an additional five activities:
6. Taking untimely meals.
7. Dancing, singing, music, watching grotesque mime.
8. Use of garlands, perfumes and personal adornment.
9. Use of high seats.
10. Accepting gold or silver.
There is also a series of eight precepts which are composed of the first seven listed above, followed by the eighth and ninth combined as one. "Ordained Theravada monks promise to follow 227 precepts!"