Weapon Special Rules

Some weapons have generic special rules attached to them. These are as follows:
Ammunition. To use a weapon that has the ammunition property to make a ranged attack, you have to have the ammunition to fire from the weapon. The ammunition is stored in the correct container, such as a quiver or case for arrows or crossbow bolts, or maybe a pouch for slings & blowguns. The weapon may be used in a melee attack though it is classed then as an Improvised Weapon (see below).A sling needs to be loaded to do this.
Finesse. When making an attack with a finesse weapon, you have the choice of either using your Strength or Dexterity modifier for the attack and damage rolls. The modifier must be same for both rolls.
Heavy. Creatures who are Small or Tiny have disadvantage on attack rolls with heavy weapons. A heavy weapon's size & bulk makes it too large to handle effectively for these sizes.
Light. A light weapon is small and easy to handle, making it ideal for use when fighting with two weapons.
Loading. Because of the time required to load this weapon, you can fire only one piece of ammunition from it when you use an action, bonus action, reaction to fire it, regardless of the number of attacks you can normally make.
Range. A weapon that can be used to make a ranged attack has a range on it's list entry. The first is the weapon's normal range in feet, and the second indicates the weapon's long range. When attacking a target beyond normal range, you have disadvantage on the attack roll. You can't attack a target beyond the weapon's long range.
Reach. This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.
Special. A weapon with the special property has unusual rules governing it's use, detailed after this list.
Thrown. If a weapon has the thrown property, you can throw the weapon to make a ranged attack. If the weapon is a melee weapon, you use the same ability modifier for that attack roll and damage roll for a melee attack with that weapon. 
Two handed. This weapon requires two hands when you attack with it.
Versatile. This weapon can be used with one or two hands. A separate damage value appears in it's statblock.
Improvised Weapons. Sometimes the player doesn't want to attack with one of their weapons, or have them at hand. An improvised weapon is on that can be grabbed with one or two hands and used instead. Broken bottles, a table leg, even a dead goblin. The weapon  is similar to an actual weapon, or at least close enough to one that the DM will assign a specific type to it. A table leg for example is similar enough to a club to be treated as one and modifiers can be applied. One with no resemblance does 1d4 damage, and the DM applies whatever damage type seems appropriate. If it is thrown the same applies, and can only be thrown 20 feet.
Silvered Weapons. Some monsters have immunity or resistance to standard nonmagical weapons, but hurt normally by silvered weapons. Adventurers can have their weapons or ammunition coated with silver at a cost of 100 gp. This represents the cost of the silver and the skill & expertise to get this process done.
Special Weapons The following weapons are described here: Lance - You have disadvantage when you use a lance within 5 ft of an opponent. Also, a lance requires two hands when you aren't mounted. Net - A Large or Small creature hit by a net is restrained until it is freed. A net has no effect on creatures which are formless, or that are Huge or larger. A creature can use it's action to make a DC 10 Strength check, freeing itself or another creature within it's reach on a success. Dealing 5 slashing damage to net (AC 10) also frees the creature without harming it, ending the effect and destroying the net. When making an action, bonus action or reaction ta attack with a net, you can make only one attack regardless of how many attacks you can make.