Ever since Aliens hit the big screen in '86, the M41A Pulse Rifle became iconic, and a lot of sci-fi media has copied the name of the rifle for their own generic sci-fi guns, most of the time not actually understanding what a pulse rifle is actually supposed to be. Oftentimes, the name "pulse rifle" will be applied to an energy weapon, because there seems to be this idea that "pulse" means energy.
But of course, the M41A itself was not an energy weapon - as anyone who paid attention to the movie can tell you - it fired 10mm explosive-tipped caseless ballistic rounds. I feel like part of this misconception may have come from one of the earlier lines by Hudson, boasting about "phased plasma pulse rifles" (in reality, a completely different weapon).
Of course, that's not to say a "pulse rifle" can't be an energy weapon (as evidenced by the prior line), but media that feature so-called "pulse rifles" (or other "pulse" weapons) tend to only apply the name to energy weapons, while their ballistic rifles are just regular modern-esque firearms. To get to the point, a "pulse rifle" is not a name for an energy weapon, and it's not just some generic sci-fi term you can slap onto any regular gun to make it sound cool and futuristic.
The term "pulse rifle" itself was coined for Aliens because the rifle operated on an electronic "pulse-action" firing mechanism, and not a traditional firing pin. While no example has been referred to as a "pulse rifle", the concept of the pulse rifle actually does exist IRL, such as with the experimental British EIW97 assault rifle or the iconic M61 Vulcan rotary cannon - both of which use an electronic pulse to fire their rounds.
This electronic firing action (AKA pulse action) works by using an electronic pulse to ignite the primer in a round, rather than striking it with a firing pin. This removes the tiny trigger-fire delay caused by the physical movement of the firing pin, marginally increasing accuracy and allowing slightly faster continuous fire. It is also more resistant to jamming.