I'm afraid 'easily' probably won't be possible, but we'll do our best. This is a question about who God is and what He's like.
The first thing you need to know is that Christians believe God is SO much bigger than us that we will never be able to 100% understand him. Even the cleverest theologians (people who study God) struggle to get their heads around the Holy Trinity, so don't worry if you still feel a bit confused. You're not alone.
Basically, Christians believe that there is ONE God, but that God is THREE persons - the Father, the Son and the Holy Spirit. This is the difficult bit. How can someone be one, but also three? A couple of helpful things to think about are:
Water, ice and steam. Are they the same or different? Well, they're the same in essence - they are all H2O. But they work very differently.
What's 1x1x1? Still 1.
See the shape to the right of your question. This is often used to symbolise the Trinity. It looks like three interlocking shapes, but when you look closely you can see it is one completely connected shape.
So Christians believe that the Father, the Son (Jesus) and the Holy Spirit are all God, yet different persons that work differently. All of them are mentioned separately in the Bible, but they are in constant relationship with one another. Jesus says "If you have seen me you have seen the Father" (John 14: 7).
This is why the Trinity is so important to Christians: it shows that relationship and community are part of God's very nature, which (a Christian would suggest) is why these things are so important to us humans.