Blender behaves in a way designed to help make UV Editing/Texturing easy. Which can be a bit confusing at first.
When using Blender Render and the 3DView's draw mode is set to Solid and Textured Solid shading is enabled both Multitexture and GLSL behave as follows -
When you are in edit mode, you can select one of an objects UV Maps, then select an image in the UV Image Editor to associate with that UV Map. While still in edit mode selecting another UV Map will also switch the image displayed in the UV Image Editor to show the image associated with it, which will also be the UV Map and image used for display in the 3DView.
In object mode selecting a UV Map will still switch the UV Map and image used in the 3DView but not the image shown in the UV Image Editor.
When unwrapping objects this is helpful but it does override the texture setup for the material. So for the texture shown may not be the same as what gets rendered.
When the 3DView shading is set to Texture, multitexture continues to behave this way but GLSL will use the image set to be used in the texture. If multiple image textures are defined then the image used in the texture lowest in the texture list will be used and if the UV Map to use is also defined in the same texture then it will be used instead of the selected UV Map in the UV Map list.
For a material with one texture and UV Map then GLSL will look closer to the rendered result, but using multiple textures will still vary from the rendered result.
When using Cycles it can seem a bit trickier. With Texure shading it uses the UV Map selected but uses an image from the active Image Texture node (the selected -or last selected- image node in the node editor) from the objects material.
When using Material shading it gets an approximation of the images used in the material, that is image nodes connected to the output with other nodes mixed in also altering the appearance but they don't give the same result as when rendered. Any uvmapping adjustments being fed into the image nodes also effect the result seen in the 3dView.