To elaborate a little on the above, maximum level is 80. That's not where the game ends though; you could argue that's when it begins.Up to 80, you're leveling, doing your personal story, doing map events, etc. You can level by killing things, exploring, or crafting. Crafting isn't tied to your level; it has its own and you could max crafting before 80.
All of the expansions are geared to level 80 so all of a sudden, you have a lot more to do The expansions do cost, only the basic game is free. There are two major expansions currently Heart of Thorns and Path of Fire. There's also not quite as major expansions: Living World Seasons 2-4 (Season 1 can't be played as it was a live event so you only get a recap now). Early next year, another major expansion is arriving.
Then there are 9 classes. Each has 2 elite specializations which grant different abilities. A third spec for each is coming with the next expansion. So really, there's a huge emount to do even once you hit 80.