What do you mean functions of OpenGL 1.3, you mean the specification or the LWJGL class GL13? If you only want to use functions that are available only in a certain specification you'll need to create a context of that version (this will throw errors when you use a feature from a newer version).
LWJGL has different classes GLXX, each version added new features so for each release the new features were included in that GLXX class (features added in OpenGL 1.3 can be accessed in class GL13 etc).
As far as learning LWJGL itself, LWJGL is "just" a layer between the actual libraries and Java. For the majority of library (OpenGL, AL, ...) features you can find it with the same name and parameters. Occasionally there are helper functions that make it a bit easier/different to setup things like buffers.
Also note that LWJGL expects you to use ByteBuffers when passing data to the libraries instead of arrays or other Java collections.
Thank you very much for your reply. You say that creating a context for a particular version will limit you to that version. What is the alternative? Is the default for it to allow you to use all versions simultaneously?
When I print glGetString(GL_VERSION) it says, "2.1.0 - Build 220.127.116.112". I would have thought that I would have a higher version since I have a fairly modern laptop and I can use the vertex, pixel and geometry shaders with Directx. With opengl, aren't the corresponding shaders only available from version 3 and up?