hi i just was messing with the render buttons and found that ray does nothing to your render but slow it down or m i missing something?
Ray enables ray tracing, which is necessary for ray shadows, ray transparency, and ray mirroring. If you don’t have these in your image, you shouldn’t have ray selected when you render.
Aaaaa… Ray enables Ray Tracing during the render. You will only notice a difference if you have materials that are set for ray tracing.
This is probably a question best posed in the Support/Composition, Visual Effects & Rendering forum OR read the Blender manual.
This Wiki entrydescribes ray tracing in mortal terms and might help you understand why it makes rendering slow.
It also passes diffuse shading between materials for objects residing on separate render layers which is really neat once you learn how to control it.
Ray also enables ambient occlusion or AO for short. It helps to add a hint of realism to your render.
It helps to add a hint of realism to your render.
…And a not so hint of render time ;D
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and is necessary for proper sub-surface scattering SSS
To sum it up - Ray (tracing) does way more than only making your render slower 
You don’t need it always so make sure to study in which cases you need it and when you can leave it disabled.
Disabling raytracing when it’s not used in the scene can still give a small speed boost since Blender doesn’t have to build the octree before rendering.
Not in Blender. Blender’s SSS doesn’t use raytracing at all.