This type of utility lets a PC be controlled via the Internet from a remote PC, iMac, iPad, iPhone, Android and many other devices.

For example, this allows Family Historian to be used remotely, or expert support provided remotely.

Such a utility not only offers remote control, but also file transfer.

Internet connections may be established via 3G, 4G, Wi-Fi, or cable.

When this page was first written, several ‘free for personal use’ utilities were available with varying features. At the time up updating (Jiuly 2020), only one of these is still free for personal use.

• TeamViewer Free for Windows PC, Linux, iMac, iPad, iPhone, Android, Windows 8/RT/Phone 8

The other two suggestions now offer Free Trials

• join.me Free for Windows PC, iMac, iPad, iPhone, Android
• LogMeIn for Windows PC, iMac, iPad, iPhone

There may be other options available.

Link: PC Remote Control