someone explain how to make redstone repeater?

one more thing they do: if another repeater or a comparator powers it from the side, it locks and holds whatever state it was in. great once you start building memory circuits, very confusing if you put two next to each other by accident and nothing works.

Top row: redstone torch, redstone dust, redstone torch. Bottom row: 3 stone. It has to be plain stone, not cobblestone, which is the bit that gets everyone first time. Smelt the cobble once in a furnace (or mine stone with silk touch) and you're set. Right click it once placed to change the delay (1 to 4 ticks), and the little arrow shows which way the signal goes.