void glBindTexture( GLenum target, GLuint texture)
Texture names are unsigned integers. The value 0 is reserved to represent the default texture for each texture target. glGenTextures may be used to generate a set of new texture names.
When a texture is first bound, it assumes the dimensionality of its target: A texture first bound to GL_TEXTURE_1D becomes one-dimensional and a texture first bound to GL_TEXTURE_2D becomes two-dimensional. The state of a one-dimensional texture immediately after it is first bound is equivalent to the state of the default GL_TEXTURE_1D at GL initialization, and similarly for two-dimensional textures.
While a texture is bound, GL operations on the target to which it is bound affect the bound texture, and queries of the target to which it is bound return state from the bound texture. If texture mapping of the dimensionality of the target to which a texture is bound is active, the bound texture is used. In effect, the texture targets become aliases for the textures currently bound to them, and the texture name "0" refers to the default textures that were bound to them at initialization.
A texture binding created with glBindTexture remains active until a different texture is bound to the same target, or until the bound texture is deleted with glDeleteTextures. When a bound texture is deleted, the default texture is bound to that target.
Once created, a named texture may be re-bound to the target of the matching dimensionality as often as needed. It is usually much faster to use glBindTexture to bind an existing named texture to one of the texture targets than it is to reload the texture image using glTexImage1D or glTexImage2D. For additional control over performance, use glPrioritizeTextures.