Half Dragon, Half Man?
Different races in this game come pre-equipped with their own skills and knowledge of the world.
For example, elves can see in the dark, halflings can pass through the legs of bigger entities and humans, while not being extra special like the others, are still very adaptable with the ability to learn quickly.
Some races give certain atrribute bonuses like the dwarves having +2 to their Constituition ability score. And some races like the ever powerful Dragonborn race, can use Dragon Breath, breathing fire, ice, poison and etc depending on what Dragonic Ancestry you chose.
That's not all hovwever. Interactions with the NPCs may also differ depending on what race you are.
As the races themselves have different opinions of each other with some races not even getting along with one another. Or worse, communications cannot even occur as a language barrier may appear as the races themselves have differing knowledge of the languges in the world.
I highly recommend reading up on the "Player's Handbook" for specifics and more details.
Favor the sword or magic or both?
Your class will play a big role in how your adventure will turn out as this will set in stone what you'll be doing most and your usual behavior for both combat and outside of combat for the rest of your adventure.
If you like charging in to solve your problems with brute strength and atheletics, swinging your weapon around wildy when fighting enemies and taking in full frontal damage with your heavy armor or sheer willpower like the tank that you are, then you might want to be a Fighter, a Paladin or a Barbarian.
Or maybe you don't like the attention, preferring to confront problems with guile or striking from the shadows? A rogue or a ranger might be right up your alley.
How about simply just supporting your teammates and party members, healing them with medicine and holy magic or rejuvenating them with a good hearty song? Clerics and Bards are another way to play too.
Or maybe you have an interest in the arcane realm and the mystical arts it brings, preferring to solve your problems with intellect and distengrating your enemies with fireballs? If that's the case, mages like Sage and Warlock might have the answer for you.
Whichever you choose, know that while every class is powerful and unique in their own ways, no one can stand on their own and you and your party members would have to cover each other's shortcomings to ensure a successful adventure where everyone comes home alive.
Of course, I wasn't able to cover all the classes as I couldn't possibly hope to do but the "Player's Handbook" has all the details on every class there is so I highly recommend checking it out if you're interested.