Explaining 5e mechanics in as few words as possible

• In 5th edition, your attributes give a bonus. 
• When you try something you roll a d20 equal to or higher than a target number. 
• If it is combat the target number is armor class. 
• If you are in advantageous situation you get to roll twice and take the highest roll. 
• If you are at a disadvantage you roll twice and take the lowest. 
• If you are proficient in a weapon, tool, or skill you get to add a bonus based on your level. 
• Hit points are considered a measure of fatigue as well as injury and every character can "take a knee" for an hour and regain a small amount of hit points. 
• The ability to "take a knee" erodes unless you have extended downtime. 
• As you level you have the option of increasing your ability scores or taking a feat. 
• Saving throws are based on the six attributes and rolled using a 1d20 equal to or greater than a target number. 
• Initiative is a d20. 
• Combat rounds are six seconds, and consist of a move and a action. 
• If you roll a nat 20 you double the dice of damage rolled (not the bonuses). 
• If you rolled a nat 1 you missed.
• Spell casting has slots that you use up during the day and are only reset after a 8 hour rest.
• You don't memorize specific spells for specific slots. Instead you prepare a limited list of spells that you can cast from during the day.
• Many spells are designed to be cast through higher level spell for greater effect. For example there is only one cure spell which heals for greater amounts when cast through a higher level slot.
• The rest are class details which are as about as complex and detailed as ADnD 1st sub classes like the Druid, Monk, or Ranger.
• To hit bonuses and Armor class have a limited range and are scaled on a absolute scale rather than by challenge level. This is called bounded accuracy.
• Higher level creatures and character are tougher because they have more hit points, do more damage, in more ways, and have more chances of attacking.