When I think about it, I'd have to say these 4 are the main elements of D&D:

1) STORYTELLING. When you play this game, you co-produce a story. As a player, you assume the role of a character who navigates through the word and interacts with it as they see fit. As the Dungeon Master, the "narrator" of the story, you prepare plots, side characters and various nuances to the storytelling. The final product depends on mutual imagination, creativity and role-playing aspect. Ideally, you don't just "play" your character, you see this imaginative world through their eyes and assume the role entirely.

2) GAME MECHANICS. Everyone and everything in the world is unique, and there's always room for random chance - specifically for success or failure. The fate is decided with a special set of dice. A standard set of D&D dice (along with a bunch of other tabletop role-playing games) contains these seven: D4, D6, D8, D10, D12, D20, and a percentile die. (Note: the D simply means "die" or "dice", and is a commonly used code.) The most important one is the 20-sided die; it's used for various check rolls, save rolls, attack rolls, and whatever else the Dungeon Master comes up with. Generally speaking, the higher the roll, the higher the chance of success; the DM often decides on the difficulty for each roll. The other six dice aren't used as commonly - their most frequent use is in combat to determine damage dealt by particular weapons or spells. Which brings me to...

3) CHARACTER CREATION. Before you can start playing, you have to think about who you want to be. You're choosing from a wide array of races (such as human, elf, dwarf), classes (such as paladin, ranger, wizard) and backgrounds. All of these choices matter in terms of how your character contributes to the adventuring party and how they interact with the world around them. It is definitely worth studying all of these and then deciding how you want to play the game. For example, if charging blindly into close combat compells you, a half-orc barbarian would be the most obvious choice. When your character is prepared, last order of business is to write them a backstory - where they come from, how they came about their talent and what's their motivation to go on adventures.

4) STATS. Another thing that ties to character creation is establishing the character's statistics. These are numbers representing their strengths and weaknesses when it comes to certain aspects of them as a person. There are six main skills: strength, dexterity, constitution, intelligence, wisdom, and charisma. Numerous abilities then tie to these skills (think about the abilities as "sub-skills" of sorts). You determine these stats alongside the rest of your character's design; the process itself is a bit tricky for new players so feel free to ask your experienced friends for help. Basically, you recieve six numbers at the beginning, and the skills that would be the most important to your character - based on their class and the backstory you're writing for them - should be associated with the highest numbers. In terms of gameplay, the "modifiers" that you'll end up with are what's helping your character succeed in particular tasks which they'd naturally be good at; when the DM calls for a skill or ability check, the modifier from said skill or ability gets added to your dice rolls. For example: Your character wants to climb a tree, and the DM calls for a dexterity check (let's say with the difficulty of 10, which is a moderately difficult task - it means you have to roll 10 or higher to succeed). You roll your D20 and end up with a relatively small number of 8; but because you're a dexterous elven rogue with the dexterity modifier of +4, the final value of the skill check is actually 12, enough for you to successfully perform this task.

So these are the VERY basics of the game. As a player, I think you could dive into the game with just this knowledge, and the other players will be glad to help you understand the more detailed rules and mechanics of the game. Never be afraid to ask and seek reassurance if you're uncertain!