When believers die they live eternally with God in heaven ("heaven" is simply defined as "the place where God is").

When Jesus was dying on the cross, one of the criminals crucified next to Him said “Jesus, remember me when you come into your kingdom”, and Jesus answered him “Today you will be with me in paradise” (Luke 23:43). The most straight forward meaning of this verse is that the criminal would immediately go to be with Jesus in Heaven when he died.

The apostle Paul seems to believe this when he says “For to me, to live is Christ and to die is gain. If I am to go on living in the body, this will mean fruitful labour for me. Yet what shall I choose? I do not know! I am torn between the two: I desire to depart and be with Christ, which is better by far” (Philippians 1:21-23).

In John 14:1-4 Jesus told His disciples that he was going to His Father’s house to prepare a place for them, and that He would come back and take them to be with Him. These verses show us that people who believe in Jesus (John 3:16) will go to the place prepared for them in heaven when they die.

The destination of unbelievers is hell ("hell" is simply defined as "the place where God is not").

The story of the sheep and the goats in Matthew 25 shows us that those who are not right with God  will go “into the eternal fire prepared for the devil and his angels” when they die (Matthew 25:41).

2 Thessalonians 1:9 tells us that those who do not know God “will be punished with everlasting destruction and shut out from the presence of the Lord and from the majesty of His power”.

Finally, Jesus warns us against leading others into sin in Mark 9:42-50 so that we are not thrown into hell “where the fire never goes out”.

All scripture quotations from NIV84