The TextBlock control in Silverlight is used in the same manner as an ASP Label control. However, from my experience you have a lot more control with a TextBlock control.
There is some background you should know about Silverlight controls. Silverlight uses a mark up language known as XAML. The Silverlight Controls can have attributes embedded in a tag or they can be in the sub elements of a control. For example when you want to change the Text of a TextBlock control you have multiple options to do this. Here are a couple of examples.

There is some background you should know about Silverlight controls. Silverlight uses a mark up language known as XAML. The Silverlight Controls can have attributes embedded in a tag or they can be in the sub elements of a control. For example when you want to change the Text of a TextBlock control you have multiple options to do this. Here are a couple of examples.

or...

Both of these code blocks will do the exact same thing. Explore through the attributes to see what you can get out of them. You can create a bit more robust text with some effort.
You can put your own creative spin on Text in a text block without having to go in to the code behind to do something really crazy like this...

So you can see that there is some great power behind the embedded tags on the XAML side. Check out all the different options that you have available to build some very robust Labels.