If you're wondering whether you can improve the performance of your headphones with a headphone amp. The short answer would be: Yes!
Depending on your headphones, there's a really good chance a quality headphone amplifier can breathe new life into your music.
A headphone amp is basically a low powered version of a power amplifier which improves the low-voltage audio signals from your source device (whether that be a smartphone, computer or turntable, etc.) to a level that can be easily and accurately converted into sound waves by the speakers inside your headphones.
While most devices already supply some power to the headphone jack, the quality of those built-in components can vary greatly and depending on the quality of your headphones, you could be missing out on a whole next level of audio quality.
Impedence also plays an important part in whether you will need a headphone amp. Headphones can range in impedence from around 16 ohms all the way up to around 600 ohms and the higher the impedence, the more amplification you will need to make those headphones work as expected. Some headphones can actually require a headphone amplifier to function, but many professional level headphones can still benefit from a headphone amp.