"Now the parable is this: The seed is the word of God.
Those by the way side are they that hear; then cometh the devil, and taketh away the word out of their hearts, lest they should believe and be saved.
They on the rock are they, which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away.
And that which fell among thorns are they, which, when they have heard, go forth, and are choked with cares and riches and pleasures of this life, and bring no fruit to perfection.
But that on the good ground are they, which in an honest and good heart, having heard the word, keep it, and bring forth fruit with patience."
This is an explanation of the parable of the sower. The text of the parable is in verses 5-8 if you want to look it up. These are all things that can happen to us as we listen to God. Sometimes we love Satan more than God, and we let him take the truth away from us... it's often easier to live without God when you pretend that he isn't there in the first place. Sometimes we believe fervently, but don't let it penetrate into the deepest part of our souls. So when deep questions come up or something comes up that we'd rather do than read or study, or go to church... then we're out of there. It doesn't matter to us beyond that first thrill of truth. Sometimes we do believe deeply, but we let other things block out that commitment. Worry about work, school, health... riches... or pleasures of this life... these things build up in our minds and hearts until they obscure the truth, until those worries, riches, or pleasures are more important to us than the truth is, and even though both fight for our attention, God never wins, so we end up accomplishing nothing except those things that are at the forefront of our minds. And the last verse... sometimes we hear the word, and plant it deeply in ourselves, and live it, and change our lives and others' lives because of it.
I don't think that this parable is about categories. We can't point to one person and say... well, he is one of those "way side" types, and this other person... she is one of the "thorn" types... and me, I think I'm kind of a "rock" type. We can see ourselves in one category or another perhaps... but that isn't who we are. We go through all of these pitfalls in our lives... Satan tries to get us any way he can. Perhaps when we are young in the gospel he finds it easy to remove the truth from our hearts. Later, we're too excited about it for that to work, but if he can throw in a good temptation, then he has us. Even later, when we know that the truth is undeniable and we've learned how much it is a part of who we are, he can still come in and block out the truth with other things that we also care about deeply. And then, when we've finally realized that the cares of this life are nothing compared to eternity... and that the riches and pleasures of this life are fleeting at best... then perhaps we have learned to have an honest and good heart, and we become the people who keep the word and who have learned some patience. :) No matter where we are now, we can still learn a new way of dealing with God's word... and we can change ourselves and, in the process, the world around us.