Personal Assistant - definition

A personal assistant is also known as Virtual Assistant, is a feature that can assist a user to operate the device without having it nearby to touch it at all. It is a trained application that can recognize the voice that comes from the user and execute according to or complete tasks.
i.e.: You can make calls or text someone by virtual assistant without even touching the phone at all. Also, it can be used to surf the internet or play a song.
There are a few types of virtual assistants are available to develop by various brands, Apple developed Siri, Microsoft developed Cortana, Amazon developed Alexa and a few others.