WiFi is the primary method by which tablets communicate. There are others, such as Bluetooth and wired connections, but WiFi is how they connect to the internet and download content and apps, as well as enable internet-based communication such as Skype.
WiFi is essential for a tablet, and the Dragon Touch Y88X does have it. WiFi is needed to download content, but many items, once downloaded, can be used without internet access, meaning that constant internet connectivity isn’t required in these cases. Some apps and content, such as streaming videos and the occasional game, will require internet access at all times in order to work.