So, you know when you do something naughty and your mom tells you to apologize in order to make things right? Well, that's kind of what a sacrament is. It's like saying sorry to God for anything wrong you might have done or asking for his blessings.
Now, sometimes people get baptized or confirmed and they later find out that the people who did it didn't do it properly or they weren't supposed to do it at all. So, to fix that, the church might do a "conditional sacrament", which is kind of like a do-over.
It's like saying, "Hey, God. We want to make sure this person really got the baptism or confirmation they were supposed to, just in case there was a mistake before. So, we are going to do it again, just to be sure."
And if everything was done right the first time, then the second time won't make a difference. But if there was a mistake, then the conditional sacrament will make things right.