The male voice has three singing registers, similar to the female voice: chest voice, middle voice, and head voice. The difference for the male singer is falsetto — the lighter part of your singing voice that sounds feminine.
The notes in your falsetto are in the same range as your head voice, but the vocal cords are thin, like a stretched-out rubber band. Falsetto feels lighter or higher than your head voice. If you attempt to sing really high notes, you may even flip into falsetto.
Falsetto is an important area of your voice and needs to be developed to strengthen the head voice. Your head voice may be weak in the beginning of your singing training; you can explore sounds on high notes by singing in your falsetto and then later, when you have more strength, work on the same notes using your head voice.
When the muscles that create head voice get stronger, you’ll be able to sing the same notes in head voice that you originally could sing only precariously with your head voice or in falsetto. Experience the sounds that you can make with falsetto, and strengthen your falsetto.
You may hear voice teachers referring to falsetto as your head voice, but using both terms is easier so you know exactly what kind of sounds to make.