5e is a very simple RPG system, based around the maxim that a character sheet must be made of 5 e's, of which four are essentials and one is not.
They can normally go up to 5 (of course), with 3 being average for a young adventurer suitable for military service, and 2 being more typical for a nameless NPC. A beginning adventurer has 12 points to distribute between them, preferably with no zeros. They are as follows:
Endurance - covers brutish feats of strength and stamina. Also, your maximum HP is equal to your Endurance (everyone knows what HP is!).
Elasticity - covers flexibility, the most underrepresented physical attribute in RPGs. But we're also following the fine RPG tradition of conflating agility and flexibility, so to do feats of dexterity and the like, you should also use your Elasticity attribute.
Education - the brainy feats, like playing dice-chess or saying which number goes after the sequence 2.7182...
Enlightenment - the largely cerebral feats that are not usually characterised as stereotypically brainy, like solving Zen Koans, or convincing Swiper to stop swiping, or resisting stuff through sheer force of will. A fifth essential attribute was considered for covering social stuff - Empathy - but since gamers normally turn that into a dump stat, it of course was folded into Enlightenment, leaving the fifth slot for...
These are traits that aren't as easily categorised. Stuff like I have special contacts in the Royal Court, or Afraid of Snakes, or Has Sword of Swinging +3. You can write down as many Eccentricities as makes sense for your concept, so long as the GM doesn't think they'll be too easy to forget. You can enable your Eccentricities by spending Eccentricity Points, either to get a numeric bonus to relevant actions for the duration of a single Encounter, or to get a more qualitative benefit. Alternatively, if an Eccentricity is used as a justification for a penalty or an unfortunate event, you get compensated with the appropriate number of Eccentricity Points during the beginning of the next Encounter.
The strength of an Eccentricity's quantitative effect is equal to the number of points paid or gained, normally up to a maximum of three (negotiate with your GM for exceptions). A qualitative effect's significance will be evaluated by the GM, and usually should range from 0 (a purely cosmetic effect that's not even good for showing off) to 5 (something that turns around a whole campaign).
You gain five Eccentricity Points at the start of an Evening of Gaming (what oldschool RPGers call a session), and you can store up to twice that number. Gaining any more than that is lost.
An Encounter is the default unit of story pacing, comparable to a scene in a film. During it, when in doubt about what happens, you'll be rolling dice to find out. All rolls are
2d6 + relevant Essential + any modifiers from enabled Eccentricities = result.
Then compare your roll to the challenge's Ease Class, which is a number either assigned by the GM, or equal to the opponent's similar roll. A task of first-class easiness task is EC 5 - so trivial almost nobody can fail it; a typical adventuring challenge that's a 'coinflip' is EC 10; something so hard that you would call it not easy at all is EC 15.
If your result exceeds the EC, you've succeeded; if it's less than the EC, you've failed; if they're equal, then the result is inconclusive.
Engaging in Combat
This is a fantasy RPG, so of course there will be combat. In combat, players' characters take turns acting in a clockwise order, then all the GM's NPCs act in whatever order the GM prefers. Each turn a participant can engage an enemy with an attack, by making a contested roll of Elasticity. Whoever has a better result deals damage to the other equal to the difference of results. If results are equal, the initiator of the engagement may opt to either have both sides take 1 unit of damage, or disengage with no damage.
Damage is subtracted from current HP (current Endurance Points). Once you're at 0 or fewer HP, you fall down and cannot continue the combat. If you've taken an amount of damage equal to twice your Endurance (i.e. your current HP is a negative value whose absolute value equals or exceeds your Endurance), something nasty happened, like death that requires a 10-minute resurrection quest or something.
At the end of an Encounter, monastic æsthetes will meditate to heal themselves, while clerks will get out their ledgers and cast healing spells on others, conanesques will try to grit their teeth through the wounds and so on. Make an Enlightenment roll at EC 10. If your result exceeds the EC, take the difference as the number of HP healed. If you're still worried your HP is too low to risk another combat, have a noncombat Encounter, like singing a serenade to a prince on the balcony, or eating, drinking and being merry (but be wary of starting a tavern brawl).
As usual, if a system doesn't cover a topic, ask your GM to make something up. If it's good, maybe it'll be integrated into the next edition of 5e!