Source: Player's Handbook

Thanks to extensive practice with the crossbow, you gain the following benefits:

  • You ignore the loading quality of crossbows with which you are proficient.
  • Being within 5 feet of a hostile creature doesn’t impose disadvantage on your ranged attack rolls.
  • When you use the Attack action and attack with a one handed weapon, you can use a bonus action to attack with a hand crossbow you are holding.