We’re so used to touchscreens and keyboards that any other control method seems fanciful. Far-fetched, even. But not anymore.

Thanks to Alexa, Cortana and Google Assistant, you can control your devices without lifting a finger.

[Read more: Google Home vs Amazon Echo - Which smart speaker is best?]

But how do these voice assistants work? And what can they do? Read on and find out.

What is a voice assistant?

A voice assistant is a personal helper that lives in your phone, tablet, speaker, streaming box or other internet-connected device. These have exploded in popularity in recent years, and now come pre-installed on most smart devices. The most common are Amazon’s Alexa, Microsoft’s Cortana and Google Assistant.

How do voice assistants work?

A voice assistant jumps into action at the mention of a keyword. This is usually a greeting that includes the assistant’s name, like “OK Google” or simply “Alexa”. Once it’s pricked up its virtual ears, you say a command, or ask it a question. The voice assistant uses natural language processing to decipher what you said, and then either answer your question or obey your command. Simple.

[Read more: The future of technology - gadgets that are smartening up our home]

What can voice assistants do?

Lots of different things. They can connect to the internet to find out pretty much any piece of information, whether it’s how much the Earth weighs or what to do in an emergency. They can take down notes or put reminders in your calendar, just like a personal assistant, and do other helpful things like set timers and alarms, which is useful for everything from cooking to just getting up in the morning. They can also control your smart home appliances like lights, thermostats and alarms.

Amazon has opened up its Alexa voice assistant to other companies to programme for. This means that companies like Ford can make ‘skills’ for Alexa that let it play nice with its range of cars. This lets drivers start their cars’ engines from the comfort of their kitchen, just by asking Alexa. Should help warm it up before you get in for the morning commute.

What is Cortana?

Cortana is Microsoft’s take on a voice assistant, and is named after a synthetic intelligence character in Microsoft’s Halo series of video games. It’s available for Windows 10 Mobile, Windows 10 PCs, the Microsoft Band fitness tracker, Xbox One games console, Windows Mixed Reality headsets and the Android mobile operating system.

[Read more: How to make Windows 10 Cortana work for you]

What is Google Assistant?

Google Assistant is Google’s personal assistant – it’s sold as “your own personal Google”. It’s available on Android phones (either built-in directly on certain phones like the Google Pixel and Samsung Galaxy S8) or by downloading the Google Allo app, and Android Wear wearable devices. It also comes as part of the Google Home smart speaker. As well as controlling Google Assistant with your voice, you can type commands and questions for it.

What is Alexa?

Alexa is Amazon’s voice assistant. It comes as part of its Amazon Echo range of speakers, and is available as an Android app for smartphones and tablets.

[Read more: 8 amazing things you can do with Amazon Echo]