Palm sugar and coconut sugar are two different types of sugars used in southeast Asia. They are often imported to North America. Both are natural sweeteners that come from trees. Coconut sugar comes from the buds of coconut tree flowers and palm sugar is made from the sap of the sugar palm tree (also called a date palm tree). Both are collected as sap. Like the North American process to make maple syrup, the sap is boiled in enormous vats to create either a sugar paste (sold in jars or tins) or rock-like chunks of sugar also known as "jaggery". Jaggery can be made from cane sugar as well. It just means the solid, rock-form of sugar.
What They Taste Like
You will find these sugars are not as sickly sweet as refined white sugars. If you are using them for cakes or other desserts, you may need to add more to achieve the same level of sweetness. They have a nice caramel-like taste which is similar to natural molasses, but lighter. It's certainly an enjoyable taste.
Both coconut sugar and palm sugar are created and sold in most Southeast-Asian countries, including Thailand. You can purchase imported coconut sugar or palm sugar in either the soft paste form or rock form in North American Asian stores. The rock type comes in a plastic package, so you'll be able to see these "cakes" quite clearly through the packaging.
Keep in mind that the names palm sugar and coconut sugar are often used interchangeably, even on package labels. That's why it's best if you are looking for a specific type, to go by the ingredients on the package rather than the title on the label. Aside from Asian stores, you may also be able to find these sugars at many health food stores or gourmet food stores.
How to Cook With Them
The paste-like form of these sugars is easy to use and has a consistency pretty similar to honey. Just add it as you would regular sugar to any dessert you might be making. You'll want to taste-test as you go to make sure you've added enough. The hard cake-like form is more challenging to use. You can either pound it or process it into a brown-sugar-like powder or you can melt it with a little water in a saucepan to create a syrup-like liquid. The resulting taste is like a caramel-flavored brown sugar, but lighter, without any aftertaste.