These verses, from John's account of the good news about Jesus, are often taken to mean that when Jesus comes again, he will take us away from the earth, to be with him in heaven for ever:
In my Father's house are many rooms. If it were not so, would I have told you that I go to prepare a place for you? And if I go and prepare a place for you, I will come again and will take you to myself, that where I am you may be also (John 14:2-3, ESV).
It's possible to read that in this sense: that Jesus will go to heaven, then at some point in the future he will come back from heaven, and then he will take us away to be with him in heaven for ever.
Clearly, the verses are very unlikely to mean that, as the testimony of the whole Bible is that God's purpose has always been for people to live for ever on the earth. So we read of "the holy city, new Jerusalem, coming down out of heaven from God" (Revelation 21:2, ESV, emphasis added), and of the resurrection of the body (1 Corinthians 15) and the liberation of the whole of creation (Romans 8:18-23) at the return of Christ to the earth. In the picture of the Lord's royal visit to the earth (his "parousia"), we will go out to meet him in the air on his way down from heaven to earth (1 Thessalonians 4:13-18), as the Saviour comes "from heaven", to transform our bodies to be like his glorious body (Philippians 3:20-21).
So what do those verses in John's Gospel mean? There are lots of possibilities, but here are some pointers.
Jesus had spoken of the temple in Jerusalem as "my Father's house" in John 2:16, so there's certainly no immediate need to think that "my Father's house" refers to heaven.
In John 14:23 (ESV), Jesus said, “If anyone loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him." Notice the similarities with earlier in the chapter: "come" and "home" (same word in Greek as for "rooms" in verse 2). I don't think this experience—of having the Father and the Son make their home with us—is one that we will experience only when we die and go to be with the Lord. Indeed, in that section of John's Gospel, this closeness of fellowship seems to be linked with the sending of the Holy Spirit.
So, perhaps this is how we are to understand those verses (original text in bold, my additions interspersed):
Let not your hearts be troubled ... because I said that I am going. I am going to be with the Father. But it is not just I who will be able to enjoy living in the presence of the Father. In my Father's house are many rooms, so you don't need to be troubled. Many people can live in the Father's presence. If it were not so, would I have told you that I go to prepare a place for you? My death on the cross and my rising in glory will prepare a place for you: they will make it possible for you to enjoy life in the Father's presence. And if I go and prepare a place for you, I will come again in a little while, both bodily, in my resurrection, and in my Spirit, and when I am risen to the Father, I will take you to myself, by sending my Spirit, so that I will be present with you on the earth at the same time as I am present with my Father, that where I am (in the presence of the Father) you may be also (in the presence of the Father, because we have made our home with you by the Spirit).
In other words, I don't think the verses are about heaven at all, or even about the second coming. But they seem to be about believers enjoying close fellowship with the Father and the Son, through the gift of the Sprit, after Jesus has died and risen again. Of course, the verses employ the image of a house with lots of rooms. But I don't think we are supposed to think about where the house is geographically (just as we're not supposed to think about what the rooms are made of, or how you get from one room to the next, or which room the Father will be in, or whether we will live in solitary confinement for ever, etc.). The Father's house is wherever the Father is present—no longer in the "Father's house" which was the temple in Jerusalem, but in the rebuilt temple which is the risen body of Christ (John 2:21), in the living temple of Christ's people (1 Peter 2:5), in whom God's Spirit dwells (1 Corinthians 3:16). We might even reflect that these verses are not so much about believers going to heaven, as about heaven coming to earth, as the Father's presence is experienced more fully on the earth through the presence of his Spirit in his people.
(Although, having said that, a lot of John's Gospel works simultaneously on more than one level, so it could also be talking about the second coming, when the "dwelling place of God [will be] with man", Revelation 21:3.)