If we decide to go for refuge in the three jewels, we should also commit ourselves to the path we choose by keeping vows.
The one mandatory vow, always implicit in taking refuge, is not wanting to harm other sentient beings. Please note that depending on tradition and teacher, some differences can appear in the exact definitions of the vows.
Optional other vows are:
1. Not killing: refers to humans and animals; it is both harming sentient beings.
2. Not stealing: not taking what is not given; (this includes not paying taxes).
3. No sexual misconduct: refers usually to committing adultery (having sex with others when married).
4. Not lying: refers usually to not lying about spiritual attainments, but can include all lying.
5. No intoxicants; refers traditionally to alcohol, but anything robbing clarity of mind (like drugs) is usually included.
"Question: What is the difference between making a commitment by formally taking refuge (and precepts) and simply not harming? Why is the formal commitment important?
Answer: Suppose you make a commitment never to kill a dragon. Most people will never see a dragon in their entire lives; some think dragons don't exist. So, you might ask, why would anyone make a commitment not to kill a dragon? If you never kill a dragon, you aren't creating any non-virtue, yet at the same time you're not creating any virtue (merit). From the day you make a commitment not to kill a dragon, and continue to uphold that commitment, you're accumulating virtue. In taking refuge, you accumulate great virtue minute by minute as you uphold your vows.
From Chagdud Tulku: Gates to Buddhist Practice: Essential Teachings of a Tibetan Master