WhatsApp for PC is tied to your mobile phone number: The Windows version of WhatsApp uses your phone to authorize your account.
WhatsApp, by default, encrypts messages end to end for some other encrypted messenger apps, like Allo, you need to actively choose to chat using end-to-end encryption. Secured end-to-end communications: WhatsApp messages are secured with end-to-end encryption using Open Whisper Systems' Signal Protocol, which is also used in Signal's Private Messenger, Facebook Messenger, and Google Allo. It's free: WhatsApp Web is free to use and doesn't include ads. WhatsApp for PC lets you use the popular messenger app on your Windows PC and chat with WhatsApp-connected family and friends wherever they are.
The WhatsApp messaging app isn't just for iPhone and Android phones.