Order and Chaos are key aspects of the world of Tellaria. While mortals have free will, the directions they lean in might lead a god or other powerful being to take interest in them. Originally (so the myths claim, at least), the gods of Order created dwarves, goliaths, humans, and halflings, and the gods of Chaos created dragonborn, elves, gnomes, and orcs. You can use this as a general guide to inform your own alignment, but don't feel constrained by it.
A lawful character generally believes that the world of mortals should align with overarching laws and principles, much like the Order of the universe with its laws of physics and chemistry. A society of Order is defined by rules and laws that apply to all within its borders.
A chaotic character generally believes in following the dictates of one’s own heart and conscience rather than looking to universal rules. A society of Chaos is more likely to follow a leader who proves themselves the strongest, the wisest, or the bravest—and follow a new leader who successfully defeats the current one.
A neutral character is most likely to do whatever seems relevant or practical in the moment. I won't stop you from creating a character who is neutral, but I'd suggest it might be more fun to pick a side.
If you want to hear more about how to think about law and chaos in D&D, here's a good video (11 min).
Different types of magic are drawn from sources that may bend toward Order or Chaos. The alignment of divine magic is the same as the alignment of the deity from whose authority it is drawn. The magic a warlock derives from their patron works similarly.
The arcane magic of wizards, focused on a mathematical or “scientific” study of The Art, tends toward Order. This can also be the case for sorcerers who have a bloodline that traces back to giants or the Titans, but sorcerers with a draconic bloodline or those influenced by wild magic will tend toward Chaos.
Elemental or primordial magic, used by druids and rangers, is drawn from the elements of Wild Nature itself, and is thus bent toward Chaos. Some druids and rangers specialize in magic associated with one of the four elements: earth, fire, water, and air – but this is not always the case.
The gods are not particularly concerned with good and evil; the principles of right and wrong are based on mortal concerns, defined by the needs of mortals—basic needs for food, water, and shelter, and social needs for relationships with others. Mortals care about good and evil; most of the gods don't care much one way or the other.
In this campaign, you may play a good or neutral character; evil characters are not likely to “play well” with the rest of the group.