4 Bit Binary Counter / Clock Divisor
This component is usually used in retro-computing (or home made computer) to divide the clock pulses allowing to use, by example, a 1 Mhz cristal to create sub-frequencies.
The binary counters can also be used to count/accumulates the pulses or create binary numbers. The 74HC161 (or 74LS161) also allow to preload a 4 bits value... and also offers carry flag when the counted value overflows the max value. This Carry Flag can be used in order to combine two counters in order to get a 8 bits 8 bits counter.
With 4 bits, you can count from 0 to 15 (or 0c0 to 0xF).