What Is Heaven? 

Heaven is the Beatific Vision.  It is the place of eternal reward for those who receive the saving mercy of Christ.  In heaven, there is no time, no corruption, no temptation or uncleanness of any kind.  It is the abode of God, Who wants us to behold Him in all His glory in order to worship and directly participate in His Eternal Happiness. 
 

Is Heaven a Physical Place?  

Scripture implies that heaven is not a physical place, per se, yet we are certain that, in some mysterious way, both Jesus and his mother Mary are present there, body and soul.  Scripture also tells us, however, that at the end of time, God will create "a new heaven and a new earth" (Is. 65:17 and Rev. 21:21).  What this will look like, or how it will subsist is unknown to us.   We also know that every human soul will be reunited with their physical body at the Final Judgment, so there is something "physical" in God's plan for Eternity.  
 

Will We Be with Our Loved Ones in Heaven?

Yes.  All of our loved ones who join us in salvation will be known to us, present to us, and even more deeply united to us as we behold together the vision of God.  
 

Even People We Didn't Get Along With?

Yes.  Except you will know nothing but love for your personal adversaries who join us in salvation, and vice versa.  
 

Worshiping God All the Time Sounds Boring.  Is That All There Is?

The Beatific Vision will be anything but boring.  We will not be sitting dumbly like statues, but instead so connected to God, we will have eternal experience, learning, and delight.  We will never exhaust the depth of God's love and knowledge, and so there will never be a "boring" moment.   We will have the ultimate freedom because we will no longer be restrained by sin.   The mystery of heaven is beyond our comprehension.  As Saint Paul wrote: 
 

“What eye has not seen, and ear has not heard,
and what has not entered the human heart, 
what God has prepared for those who love him,”
this God has revealed to us through the Spirit.

(1 Corinthians 2:9-10)

Does Anyone Go to Heaven Directly?

Among creatures, only the Blessed Virgin Mary certainly entered heaven directly.  The Church does not stipulate that even canonized saints have gone to heaven directly, only that they've entered (at some point).  We can be morally certain that a baptized child prior to the age of reason, and therefore not culpable of sin, would achieve nothing in purgatory, and go directly to heaven, although there is no hard and fast teaching.  

Saint Thomas Aquinas taught it's a certainty that any individual (at any age) who dies immediately after receiving baptism goes directly to heaven.  Moreover, the Church has traditionally offered reasonable certainty, through her funeral rites, that a deceased, baptized child incapable of sin is already in heaven.  But there is nothing official on this subject.  
 

What About Unbaptized Children, Infants, and the Unborn?

The Church teaches that we entrust the souls of unbaptized infants, young children, and the unborn to the mercy of the Father in heaven.  The Church speculated for many centuries on the possibility of "Limbo", or, a place that is technically the "outer edge" of hell, which is a place of no physical suffering, and a place of perfect natural happiness, yet deprived of the Beatific Vision.  This was never considered an infallible doctrine, but the faithful are permitted to hold that belief.  The idea of Limbo began to fall out of favor in the 20th century, as the Church contemplated that it would be more appropriate for God's baptismal grace to extend, in some way, to infants and children who, through no fault of their own, did not receive Baptism.  This presents its own difficulties, as the Church maintains a dogmatic belief that Baptism is necessary for salvation.  Nonetheless,  we are called to Hope in God's mercy for them, as the proper attitude for Catholics until such time as the Holy Spirit clarifies this question.   In short, we acknowledge that our cooperation with salvific grace is confined to the sacraments, but God, Himself, is not limited by the sacraments and may accomodate these souls out of His limitless Mercy.   
 

Will I Be Upset That I Have Less Glory in Heaven Than Another?

No.  We will rejoice in the glory of those who were worthy of it by virtue of their saintly lives, because in doing so we will be rejoicing in God's work.  There is no temptation to sin in Heaven, and therefore, no pride.  We will each be satiated with joy and glory to the extent we are able to receive it.  If we want a bigger vessel to hold greater glory, we need to work toward that while we are among the living.  But there will be no loss or regret once we enter the Beatific Vision.