How shader files work:

When you call shader's Load function, you give it two filename.  The first one is the base name of the vertex shader, the second is the base name of the fragment(pixel) shader.  You may pass an empty string("") for either file, if you only want one type of shader.

For example, to lead the land's vertex and fragment shader, pass the filename "data\shaders\land_full" for both entries.

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The file naming can be broken into two parts: The name, and the extension.

The extension is automatically appended by the shader class to the base file name.  They are as follows:
Vertex Shaders:
 >Directx = .hlsl_v
 >OpenGL = .glsl_v
Fragment(pixel) Shaders:
 >Directx = .hlsl_f
 >OpenGL = .glsl_f

The .hlsl_* files are written in MS's High Level Shading Language.  At the start of vertex shaders in HLSL, always put the line: #include "hlsl_v_base.hlsl"
The .glsl_* files are written in the OpenGL Shading Language, version 110.

The filename should describe the intended use of the shader.