A list and information on various ways to play online.
Roll20:One of the more popular VTT available. It is a hosted/SaaS service that is browser based so people can play from many different devices. It start out with a free level service and has two higher level subscriptions that add additional storage space and features such as macro and API access.
Beyond20: This is an browser extention for Chrome which allows you roll attack, saving throws, skills, etc. directly from a D&D Beyond character sheet and have the results show on Roll20's chat window. Also works with Foundry VTT and Discord.
VTT Enhancement Suite: A browser extentions for Firefox and Chrome that provides user interface and functionality improvements to Roll20.
Fantasy Grounds: Another very popular VTT. It is a installed application with a server-client architecture so all the data and control is done through the host (GMs) computer. It has both one-time and subscription licensing of two different levels; Standard (all people must have Standard or higher license) and Ultimate (only the GM needs a license).
Tabletop Simulator: This program isn't specific to RPGs, and approaches VTT in fairly literal manner (there's even a VR option). The cost is $19.99 (but it is frequently on sale for less), and requires each member of your group to purchase the program. After the initial purchase, there are many free options and assets to customize your gaming space for your particular game of choice. There are many free prepackaged sets for playing D&D and other specific RPGs if you don't want to do all the work yourself. Includes its own of VoIP, but can be used in combination with others, like Teamspeak, Discord, etc.
Astral Tabletop: Appears to be endorsed by DriveThruRPG. One of the easier VTTs to use. Support most editions of D&D, and a host of other RPGs. Free, with paid upgrades for more features and increased storage space.
D20PRO: A multi-platform VTT specialized in D&D, Pathfinder, and Starfinder.