The Catechism in Questions & Answers

189. What is the resurrection body of Christ?

The resurrection body is liberated from finiteness and mortality. It is no longer bound to space and time. The resurrection body of Christ is a body that never becomes sick, never ages, and never dies. It is a glorious body.
It was in this glorious body that the Lord appeared in the midst of His disciples. He walked through closed doors, broke bread with the disciples, showed them His wounds, and ate with them. Thereby He made it clear that He was not a “spirit” but rather that He was physically present with them as Jesus Christ.
“Resurrection” does not signify a return to earthly existence.

Resurrection: see Questions 535., 559.

“Then, the same day at evening, being the first day of the week, when the doors were shut [...] Jesus came and stood in the midst.”
John 20: 19

“‘Behold My hands and My feet, that it is I Myself. Handle Me and see, for a spirit does not have flesh and bones as you see I have.’ When He had said this, He showed them His hands and His feet.”
Luke 24: 39, 40