Generally speaking, you'll need a modern computer, laptop tablet, or mobile phone with an up-to-date processor. For the more technical minded, the tech specs can be found below:

Windows
1.4GHz Intel® Pentium® 4 or faster processor (or equivalent) for Microsoſt® Windows® XP, Windows 7 or Windows 8, Windows10;
2GHz Pentium 4 or faster processor (or equivalent) for Windows Vista® Windows XP, Windows Vista, Windows 7, Windows 8, Windows10;
512MB of RAM (1GB recommended) for Windows XP, Windows 7 or Windows 8, Windows10;
1GB of RAM (2GB recommended) for Windows Vista
Google Chrome 47 or above; Mozilla Firefox 45 or above

Mac OS
1.83GHz Intel Core ™ Duo or faster processor
512MB of RAM (1GB recommended)
Mac OS X, 10.5, 10.6, 10.7, 10.8, 10.9, 10.10 or above
Google Chrome 47 or above; Mozilla Firefox 45 or above

Linux
Ubuntu 10.04, 11.04 or latest; Red Hat Enterprise Linux 6
1.4GHz Intel® Pentium® 4 or faster processor
512MB of RAM (1GB recommended)
Google Chrome 47 or above; Mozilla Firefox 45 or above

Chrome OS
Chrome Book