Aham Brahmasmi is one of the four mahavakyas, meaning "great sayings" of the Upanishads.
Depending on where it is applied, aham may allude to a real ego or a false ego. While the real ego refers to the understanding of Self as a spiritual being, the false ego refers to thinking of oneself as a material body, which is temporary.
When aham is used with kara, which means "created thing," as in ahamkara, it refers to the human ego. Such ego is called the false ego.
When aham is used in the saying, Aham Brahmasmi, it refers to the real ego as it is an expression of Self-realization.