The title is a misnomer, really. No one can really fully explain the Trinity (tri-unity), the Triune nature of God: the Father, the Son, and the Holy Spirit. We have metaphors to help us grasp the concept of one God yet three Persons, but none of them fully explain it perfectly.
Still, I think it is beneficial to talk about. Hearing and coming up with pieces of explanation is quite interesting. Here are a few of the metaphor explanations I’ve heard, though do keep in mind these are only partial explanations to help you have a piece of understanding:
The Trinity can be described like a triangle. It is one triangle, but has three aspects. Take away one and it isn’t the same.
The Trinity can be compared to an egg. The egg has a shell, a white, and a yolk, but it is one egg.
The Trinity can be compared to a braid. When you have a braid you have three strands, but they are woven as one braid, and it is all the same hair.
The Trinity can be described with a math equation. It’s not 1 + 1 + 1 = 1, but 1 x 1 x 1 = 1.
The Trinity can be described using roles and relationships. A man can be a father, a son, and a husband at the same time, but still be one person.
Go study the Trinity on your own, too! While the Bible doesn’t specifically use the word “Trinity,” it does speak of the different persons of God and how they are equal and one. Go look this up! It’s awesome!