TexturesCube probleme

can somoene explainn for me what mean “cube_map.vert” and “cube_map.frag” and “u_cubeTex” in this code:

auto texturecube = TextureCube::create(“left.jpg”, “right.jpg”, “top.jpg”, “bottom.jpg”,“front.jpg”, “back.jpg”);
//set texture parameters
Texture2D::TexParams tRepeatParams;
tRepeatParams.magFilter = GL_NEAREST;
tRepeatParams.minFilter = GL_NEAREST;
tRepeatParams.wrapS = GL_MIRRORED_REPEAT;
tRepeatParams.wrapT = GL_MIRRORED_REPEAT;

//create a GLProgramState using custom shader
auto shader = GLProgram::createWithFilenames(“cube_map.vert”, “cube_map.frag”);
auto state = GLProgramState::create(shader);
// pass the texture sampler to our custom shader, state is a pointer of GLProgramState, u_cubeTex is a uniform in shader
state->setUniformTexture(“u_cubeTex”, texturecube);

also when i use skybox with folowin code it’s be without colors can somoene help?
// create a texture cube
auto textureCube = TextureCube::create(“left.jpg”, “right.jpg”,“top.jpg”, “bottom.jpg”,“front.jpg”, “back.jpg”);
//create a skybox
auto skyBox = Skybox::create();
//set cube texture to the skybox

Read API description plz