Grappling is one of those D&D rules that sounds like it should be incredibly simple. You grab somebody. They cannot go anywhere. Done.
Naturally, that means I have watched it turn into a ten-minute discussion about Athletics checks, whether you can grapple an ogre, whether grabbing someone makes them easier to stab, and whether the barbarian can drag the goblin through a campfire like some kind of medieval floor mop.
Part of the confusion is that grappling actually changed quite a bit in the 2024 rules. So, if you remember both characters rolling Athletics and comparing the results, you are not imagining things. You are just remembering the older version of the game.
Under the current rules, you normally grapple someone through an Unarmed Strike. Instead of using that Unarmed Strike to deal damage, you choose to grapple them.
There is no attack roll involved. The target makes either a Strength or Dexterity saving throw, and they get to choose which one. The DC is 8 + your Strength modifier + your Proficiency Bonus. If they fail, they are Grappled.
You also need a free hand, which makes sense considering you do, in fact, need to grab the person somehow. The target can also only be one size larger than you at most. A Medium fighter can grapple a Large ogre, but they cannot stroll up to an Ancient Dragon, grab its ankle, and declare that its Speed is now 0. I appreciate the confidence, though.
Once someone is Grappled, their Speed becomes 0 and cannot increase.
This is the main point of grappling. You are stopping someone from moving.
However, this is also where people tend to give the Grappled condition a bunch of powers it does not actually have. Grappling someone does not make them Prone. It does not give everyone Advantage when attacking them. It does not stop them from attacking you, and it does not stop them from casting spells.
In fact, a Grappled creature can continue doing most things normally. The big difference, besides being unable to move, is that they have Disadvantage on attacks against anyone other than the creature grappling them.
So, if you grab the enemy wizard, they can still cast a spell. If that spell requires an attack roll against somebody else, they have Disadvantage. If they decide to attack you instead, the grapple itself does not impose that Disadvantage.
That said, grappling becomes much nastier when you start combining it with other things.
The obvious one is Shove. If you knock a creature Prone and then grapple it, its Speed becomes 0. Normally, standing up from Prone costs movement equal to half your Speed, but you cannot stand up while your Speed is 0.
Now you have someone lying on the floor who cannot simply stand back up until they deal with the grapple.
This is why grappling can actually be very useful even though grabbing someone by itself does not give you Advantage. The Grappled condition is fairly limited, but stopping movement lets you set up all kinds of other nonsense.
You can also drag a Grappled creature with you. Normally, every foot you move while dragging or carrying them costs an extra foot of movement. So, with 30 feet of movement, you are generally getting about 15 feet while dragging someone around.
There are exceptions if the creature is Tiny or at least two sizes smaller than you, but for most normal fights, assume dragging your unwilling new friend slows you down.
And yes, this means players will immediately start looking for cliffs, lava, Spike Growth, campfires, holes, suspiciously placed meat grinders, etc. At that point you are no longer really dealing with the grapple rule. You are dealing with whatever horrible idea your players have attached to it, and you rule the interaction from there.
Getting out of a grapple works a little differently from resisting one in the first place.
A Grappled creature can spend its action to make either a Strength (Athletics) or Dexterity (Acrobatics) check against the grapple’s escape DC. If it succeeds, the grapple ends.
Notice the slightly weird distinction there. When someone initially tries to grapple you, you make a Strength or Dexterity saving throw. Once you are already grappled and try to escape, you make an Athletics or Acrobatics ability check.
That difference is easy to miss, especially if you played under the older rules where Athletics and Acrobatics were involved from the start.
The grapple also ends automatically if the grappler becomes Incapacitated or if something moves the two creatures far enough apart that the grapple is no longer possible. The person doing the grappling can also simply let go whenever they want. No action required.
There is one more fun interaction worth knowing. An Opportunity Attack can be made with an Unarmed Strike, and an Unarmed Strike can be used to grapple. So, yes, under the current rules you can potentially grab someone as they try to leave your reach. If they fail the save, their Speed becomes 0, which can ruin their escape rather quickly.
Ultimately, grappling is much less complicated than it tends to become at the table. You use an Unarmed Strike, the target makes a Strength or Dexterity save against your grapple DC, and if they fail, their Speed becomes 0. You need a free hand, you cannot grapple something more than one size larger than you, and dragging them usually costs extra movement.
Just remember that Grappled means grappled. It does not secretly mean Grappled, Restrained, Prone, Silenced, Helpless, and Having a Really Bad Tuesday all at once.
