With the load on the collector, the configuration is called "common emitter amplifier".
This circuit provides both voltage gain and current gain.
A base-emitter voltage (Vbe) greater than 0.7V will turn on the transistor as a switch.
The standard practice is to use a current gain (beta) = 10. Hence if you want to switch 100mA through the load, make sure the source driving the base current can provide 10mA, i.e. Ib = Ic/beta.
A "common collector" or "voltage follower" configuration is used when you need to match to a low impedance load.
There is no voltage gain and Vb (voltage at the base) must exceed the voltage out at the load.