There is a belief, held by some, that when a person dies their body and soul lie in the grave awaiting the resurrection; this belief, however, is not supported by Scripture.
Prior to Christ Jesus' ascension to heaven (forty days after His resurrection), the immaterial side (the soul and spirit) of all who died went to a place in the heart of the earth known as Hades, or Sheol.
One area, known as Abraham's Bosom (or Paradise), was where Old Testament saints (people of faith in the one true and eternal God) went. It is, also, where those who died, having never reached the age of accountability, went.
In Abraham's Bosom, the righteous dead were awaiting Christ Jesus' victory over sin and death on the cross of Calvary as the perfect Lamb of God that takes away the sin of the world.1
When Christ Jesus ascended to heaven forty days after His resurrection, He took those held captive in Abraham's Bosom (the righteous dead) to heaven with Him; Paradise is now in heaven.2 The other area in Hades is where the un-righteous dead still reside.
Now, when a Christian or one who has not reached the age of accountability dies, their immaterial side (their soul and spirit) go to be with the Lord in heaven.3
At a future date in time, they will be resurrected from the grave and will receive imperishable, glorified bodies that will never more grow old, get sick, or die. At that time, their body, soul and spirits will once more be re-united.
Also, at a future date in time, all of the un-righteous dead will likewise be resurrected and their body, soul, and spirits, will be reunited. The righteous will spend eternity with God, and the un-righteous will spend eternity separated from God in a place of torment known as the lake of fire.4
1 (Luke 16:19-31; 1 Peter 4:6)
2 (Ephesians 4:8; 2 corinthians 12:2-4)
3 (2 Corinthians 5:8)
4 (Revelation 20:11-15; 21, 22)