Original: In the epilogue to Deathly Hallows, set nineteen years after Harry defeats Voldemort, Harry has named his second-born son Albus Severus, after Albus Dumbledore and Severus Snape.
Simplified: Later, Harry Potter and Ginerva Weasley named their youngest son after Albus Dumbledore and Severus Snape. Harry confesses to his son Albus Severus that Severus Snape was the bravest man he ever knew even though while still at school, Snape had been the teacher that Harry had hated the most because of Snape's bad behavior towards Harry.