Q. What are the four noble truths?

According to the Essentials of Philosophy and Ethics The Four Noble Truths are:

The Four Noble Truths The teaching of the Buddha has been summed up in the Four Noble Truths which are:

• dukkha (suffering, unsatisfactoriness)
• samudaya (arising of suffering, origin of suffering)
• nirodha (cessation of suffering)
• magga (path).

Of course this is not a complete explanation, you should read the full article and you should read other articles on the topic.  There are slightly different versions of the truths depending on which text you read and which sect of Buddhism you are reading about.