From publisher blurb:
Dungeons & Delvers is a tabletop role-playing game that focuses on the classic model of exploring dungeons, fighting monsters, and looting treasure. It's geared towards younger gamers, but fun for everyone!
This version of Dungeons & Delvers uses a dice pool mechanic. An adventurer’s stats and skills are measured with dice: a d4 is the lowest you can go, and represents either a poor stat or being untrained at a skill, and everything caps at a d12.
When you want to do something (and the GM isn't certain of the outcome), you pick the most relevant stat and skill, roll both dice, and compare the total against a target number. If you meet or beat the target number, you succeed. Otherwise, you fail.
Dice pools can contain more than three dice, usually due to race or class talents giving you extra dice when doing specific things. You roll all of your dice, but only ever choose the two highest results.
As with most fantasy dungeon crawlers, an adventurer is largely a combination of a race and class.
Your race gives you a racial talent to reflect the nature or abilities of that race. Each race has access to more than one talent: for example, dwarves can start with an additional Wound, be resistant to poisons, or better wield axes and hammers.
Your class determines your starting stats and skills, what weapons and armor you can use without suffering penalties, what gear you start with, and how many Wounds you can suffer before getting knocked unconscious. Classes also start with one or more class features and/or talents that reflect what the class can do or is particularly good at.
The core book features a diverse collection of people and creatures, but there is also plenty of advice on creating your own.
Monsters are essentially simplified adventurers: since part of the GM's job is controlling all of them this makes it easier to handle.