An ordinary 555 timer IC has ordinary bipolar transistors, needs a min supply voltage of 4.5V, has a fairly high operating current and has a high sink or source 200mA output current.
A Cmos 555 timer IC has Mosfet transistors, needs a min supply voltage of only 1.5V, has a fairly low operating current and can sink only 50mA and source only 10mA when its supply voltage is high with a fairly high voltage drop.
Cmos 555 timers have parts numbers like:
ICL7555, TS7555, LMC555 and TLC555.