So you bought Destiny 2, but there are seasons and DLC and the Eververse and people just bandy names of strikes around like you know exactly what they are talking about. It can get a bit confusing thanks to things being a tad unclear. Bungie plans to make a clear distinction so that you know what costs money and what costs time.
The picture shows the clear distinction between paid for and free. Expansions are bought and include new campaign and strikes, a new destination with rewards, new raid lair, new crucible maps and new legendary and exotic gear. Seasons are available to all Destiny 2 players, which includes Iron Banner, Faction Rallies, Seasonal rep rewards, endgame playlists, seasonal events and features and updates.
This makes a lot more sense as now you know what types of content will be expansion-only and what you can keep doing without handing over more money.