This is a great mystery, but as the Heidelberg Catechism states, it does assure us that we are fully delivered from the anguish and torment of hell in Christ (Q&A 44).

Here is a general summary of the main thoughts of most evangelical theologians:

*Jesus' spirit separated from his body and...

--He entered hades to proclaim a message to disobedient spirits (1 Peter 3:18-22) ... OR .... 1 Peter refers to the Son of God preaching by the Holy Spirit through Noah to the people of Noah’s day.

--He entered paradise to appear to Old Testament believers and lead them to heaven (Luke 23:43; Ephesians 4:8).

*While Jesus was in the grave...

--His spirit was not asleep, though his body was slain.

--He did not suffer wrath in hell -- his work on the cross was sufficient (John 19:30 - "It is finished!").

--He did not offer sinners a second chance for salvation (Heb. 7:27). Once someone dies, there are no second chances (Hebrews 9:27).

Here are some links for further study. We'd encourage you to check them out:

https://rts.edu/resources/what-does-it-mean-that-jesus-descended-into-hell/

https://www.gotquestions.org/where-was-Jesus.html

https://www.ligonier.org/learn/qas/since-jesus-took-our-punishment-why-didnt-he-go-to-hell-forever