Codeweavers is a company selling a proprietary version of Wine (see :
Wine HQ), a free implementation of Windows internals allowing you to execute some Windows software. I wrote "some" because compatibility is not always perfect, so don't expect to use a Photoshop or a 3DSMax under Wine like you would under an full Windows installation.
See :
CodeWeavers - Wikipedia, the free encyclopedia for more information about CodeWeavers.
There is another company selling another proprietary version of Wine : Transgaming and its Cedega products. It's a Wine enhanced for games. See
TransGaming Technologies - Wikipedia, the free encyclopedia.
Wine is fine, and its creators comitted an enormous amount of work in it. Give a try if there is a piece of software you can't live without on a Linux box. Wine will have less overhead than a full virtualisation of Windows, but will be less reliable too. It's up to you to test which solution works better for you.