I know that my question is simple, but i have a doubt.

It's not clear about the difference between Workgroup and wavefront

At first, i have the global work size, that is the size of my work load and in principle is amount of kernels.

Local work size is the amount of kernel of each computer unit, so a work-group for each compute unit.

Is all of this aforementioned correct?

But, when i read ATI Stream Computing OpenCL, there are a concept about wavefront. There explain that wavefront is a set of work-items, and up to 4 work items can be pipelined in the stream core for processing. And, that the size of wavefront is especific of each gpu board configuration.

I think that each wavefront is for each compute unit. So, what is the function of work-group? Where i send a work-group?
A group of wavefront being a work-group, it's not clear how i will split my workload in a GPU.

I think thats my problem is concepts error.

I know that is simple my question, but it's not clear for me.