Redstone signals only travel a certain amount of blocks through Redstone Wire. A Redstone Repeater is for extending said signal. Put it at the point in the wire where the signal is getting low and it will make it go for another set limit of blocks.
They can also be used to time signals to amke things like pulses and what-not.
its simple what it does! for example you do a piston gate: you put repeaters between the redstone dusts and it will delay the signal on how much you will put its level on!
They can also be used to time signals to amke things like pulses and what-not.
the default is the shortest delay, then each click adds some delay so the output will take longer to power up
i normally don't change the delay, it's for more advanced constructions
make sure to note the arrow on the repeater, the direction the signal travels thru it is important, it's a one-way device
you can't yet ;P