In audio, ohms appear primarily in speaker impedance (4Ω, 6Ω, 8Ω are common) and headphone impedance (16Ω–600Ω). The impedance of a speaker or headphone must be compatible with the amplifier: connecting 4Ω speakers to an amplifier rated only for 8Ω+ can cause the amplifier to overheat or shut down.
Headphone impedance determines drive requirements: low impedance (16–32Ω) works with phones and laptops; high impedance (150–600Ω) requires a dedicated headphone amplifier for proper volume and damping. Impedance is NOT the same as DC resistance — it varies with frequency, which is why speaker impedance is given as a 'nominal' value.