your sins are forgiven

Jesus tells His disciples something interesting in John 20:23. i’m having a hard time wrapping my head around it.

"If you forgive the sins of any, their sins have been forgiven them; if you retain the sins of any, they have been retained."

what does that mean? did the apostles have the right and or ability to forgive sins or not forgive sins? i have always thought that God alone was able to forgive sins. what are your thoughts on this verse and this matter?