As the title clearly indicates, MX Player Codec ARMv7 NEON is a lightweight application, that simply deploys, on your Android device, a codec required by the popular MX Player. In simple terms, you need this package if your smartphone or tablet uses ARMv7 NEON CPUs. But, in case your device does not have this specific CPU, this codec is not needed by your MX Player.
Keep in mind that this well-known media player is very good at checking if your device is supported. Don't install additional codecs if you're not asked by MX Player.