You may have noticed that the previous example was sung first by a female voice and then by a male voice. In general, female voices are higher in pitch than male voices, although everybody’s voice range is individual and there are many variations. The "range" of a person's voice is determined by the highest and lowest notes they can sing. Vocal ranges are discussed in detail in Lesson 3.
When you are learning to copy recorded versions of songs by ear, you may feel that you have the correct notes but your version sounds higher or lower than the one you are copying. For example, if you are a female singer learning from a version of a song sung by a male singer, your version may be higher.
This is because you have a higher voice range than the male singer. In this case you are likely to be singing the notes in a different octave to the original. An octave is a measurement of distance in music which will also be explained in Lesson 3.