Like color, functions, timer.I purchased one set for a tree in our front yard. I turned them on on Thanksgiving night. They weren't super bright, the LEDs are small, but they did the trick so I purchased 3 more sets. Before the 3 additional sets got here the batteries went dead in the original set (after 6 days). I purchased rechargeable batteries for all 4 sets to avoid going thru 100 batteries by New Years day. Charging the batteries is a hassle, not to mention trapesing thru the snow in 20 degree weather to replace them every 5-6 days. I'm not sure if I'll use them again next year or opt for some long extension cords. But they do have 8 different functions to select from and the timer on all 4 sets seems to work perfectly.Only reason I rated this 4 stars and not 5 is because the lights do not use an electric outlet for power. You have to feed batteries into it every time they die. I prefer an outlet plug. However, the various light setting are fun and flash at different rates at the press of a button. Great lights but I prefer without batteries needed.Short life of batteriesA mi me encantaron .. su color las opciones que tiene para cambiar el modo de las luces y lo mejor de todo usan baterías ? así que ahorre energía y mis baterías duraron desde noviembre hasta terminar el mes completo de diciembre.. las recomiendo ?The strand is nice and long, and the lights are bright with brand new batteries in, but batteries run out quickly and the lights are tiny. These lights are a nice accent to your tree, but they will not brightly light it up. I ended up having to buy more lights to get the brightness I was looking for.Best feature, we used them in a south facing window, indoors, and during the power outage we had some of the only functioning Christmas decorations for the neighborhood. This is an idea worthy being further developed.