A subscription is not required to use D&D Beyond - you can use all of the features and unlock all the official content with a free account.
Players can get the most out their D&D Beyond experience by signing up for one of two subscription tiers.
The Hero Tier is intended primarily for players. It removes ads on the site, allows players to create an unlimited number of characters, and add publicly-shared homebrew content to your collection to use within the toolset. This subscription will cost $2.99 a month.
The Master Tier is intended primarily for Dungeon Masters and full groups. It grants all the benefits of the Hero Tier, and also allows a DM to share all her unlocked official content with other players within a campaign - so content does not have to be unlocked by every player. This subscription will cost $5.99 a month.