Usually, the last two are the model(and the range of the gpu) and the other are the lineup(the technology).So basically gtx1050 and gtx1080 use the same "Nvidia's Pascal" technology, but gtx 1080 is far superior because its a better and more expensive/high-end model. So a gtx980 (which uses the older "Nvidia's Maxwell" technology) is worse than a gtx1080. You should always check benchmarks tho, because newest technology isnt always better when comparing different models.An example is, that a 970 is better than a 1050.