hFE of a transistor is the current gain or amplification factor of a transistor.
hFE (which is also referred to as β) is the factor by which the base current is amplified which is fed into the transistor.
A transistor works by feeding a base current into the base of the transistor. The base current is then amplified by hFE to yield its amplified current. The formula is below:
IC= hFEIB=βIB
So if 1mA is fed into the base of a transistor and it has a hFE of 100, the collector current will be 100mA.
Every transistor has its own unique hFE. The hFE is normally seen to be a constant value, normally around 10 to 500, but it may change slightly with temperature and with changes in collector-to-emitter voltage.
Check the transistor's datasheet for the hFE value in its specifications.