D&D Classes TL;DR

Artificer: "Makers of magic-infused objects, artificers are defined by their inventive nature. They see magic as a complex system waiting to be decoded and controlled. Instead of ephemeral spells, they seek to craft durable, useful, marvelous magical items."
Experts in crafting and utilizing magical items, Artificers can specialize to create potions, use magic-fueled wands and turrets, firearms, utilize and create arcane AI, or equip themselves with a mechanical companion to fight alongside them. They're incredibly flexible, and are centered around their ability to utilize these items better than others, along with the ability to produce them. Machines are, after all, man's best friend.

Barbarian: "A fierce warrior of a primitive background who can enter a battle rage."
Barbarians focus on strength and bulk, and are all about brawn and overpowering their enemies. Their battle rage allows them to halve any slashing, piercing, or bludgeoning damage, so long as they maintain it by hitting things.

Bard: "An inspiring magician whose power echoes the music of creation."
Bards are typically a jack-of-all-trades figure, and can do any mix of spellcasting or physical prowess. They have strong utility, and are incredibly flexible.

Cleric: "A priestly champion who wields divine magic in service of a higher power."
Clerics are typically somewhat bulky, and can either focus on dealing damage or heal. They pledge their lives to a divine power, and draw their power from their deity.

Druid: "A priest of the Old Faith, wielding the powers of nature — moonlight and plant growth, fire and lightning — and adopting animal forms."
Pretty straight-forwards. Druids are spell-casting combatants, and can choose to forego their emphasis on spells in order to instead focus on their ability to transform into creatures. They hate metal, and will abstain from using it. Ye ol' nature hippy.

Fighter: "A master of martial combat, skilled with a variety of weapons and armors."
General, all-around martial combatants. Old-fashioned learn-to-fight. Some of them can even tap into spellcasting.

Monk: "A master of martial arts, skilled with fighting hands and martial monk weapons."
Utilizing their Ki, a Monk is a fast-moving and evasive martial combatant. They follow some path to spiritual awakening, or something like that.

Paladin: "A holy warrior bound to a sacred oath."
Paladins are all-around brawlers, and lean towards the bulkier side of things. They have access to some spellcasting, can use weapons, and can do a bit of healing. They're bound to a sacred oath, which they must never break.

Ranger: "A master of ranged combat, one with nature."
Rangers are ranged combatants, who specialize in traversing the wilderness, survival, and general bow usage.

Rogue: "A scoundrel and agile warrior who uses stealth and trickery to overcome obstacles and enemies."
Squishy, high-burst fighters who use their skills in order to manipulate and get into position. Generally good at stealing things, lying, and stealth.

Sorcerer: "A spellcaster who draws on inherent magic from a gift or bloodline."
A squishy caster who has innate power they draw upon. They can bend this power to their whim, and are very flexible in how they can cast their spells.

Warlock: "A wielder of magic that is derived from a bargain with an extraplanar entity."
Pact-making spell casters. At the cost of the ability to cast very few spells, their basic spells are much stronger, and they regain their used spells on a short rest.

Wizard: "A scholarly magic-user capable of manipulating the structures of reality."
Typical wizards; they learn magic, and can add it to their spell book, while choosing a specific school of magic to hone in on and specialize in.