What is a vocation? In the book Brideshead Revisited by Evelyn Waugh, a character named Cordelia describes it as this, "It [Vocation] means you can be a nun. If you haven't a vocation it's no good however much you want to be; and if you have a vocation, you can't get away from it, however much you hate it."
Now this particular quote refers to religious life, but you can also apply this to marriage, the single life or priesthood. However, this "type" of vocation is not the only one. There are actually three types of vocation. (I know, mind-blown) The first is the primary vocation. This is the vocation to Christ, "fully actualized in Catholicism." This type of vocation applies to all ages and is not restricted to adulthood.
The second is much the same as Cordelia mentioned above. It is the vocation to religious life, marriage or the single life. A special note about this one: Yes you have a specific vocation hand-selected for by God, but don't fret if you choose the "wrong" one. God will still love you and will work with you where you are.
That being said, the vocation that you are actually called to, you will probably feel happier and more peaceful in, but God will love you no matter what. The third type of vocation is that of your vacation. If you know me, you've perhaps heard me call teaching a mission or a calling of mine.
I didn't just one day say: "I'm going to be a teacher because I don't know what I want to do." No. I decided to become a teacher because not only was I inspired by teachers I had, but I felt a sense that I'm called to teach. Not only do I feel called to teach high school (so teenagers!). So this would be my third vocation, which is to the occupation. So as a recap of the three vocations let's walk through what mine are.
My first vocation is that to Christ which is fulfilled through the church and through a personal relationship with Christ. This is a vocation that is what you'd perhaps call universal. Which means the type of vocation is meant for everyone.
The second is that of a calling to religious life, marriage or single life. At the young age that I'm at in my life, I have not discovered what my vocation is in this type. If you are in the same boat as me, don't fret. God will reveal his plan for you in his time. God has shown me by not showing me, that it is not time for me to know my second vocation.
The third and final vocation is that of your occupation. Now this one is one that changes. What do I mean by this? Well, it changes based on what stage in life you are. For example, as a child and even now as a young adult, my vocation is to be a student. I've discerned and discovered that my vocation after being a student is to be a teacher. I hope this is helpful in your discernment and your understanding of what a vocation is.