Explain two reasons why the trinity is important to christians?

Because first of all the trinity (when we do it) it is in the shape of the cross (in which Jesus died)

And second of all The Christian doctrine of the Trinity (Latin: Trinitas, lit. 'triad', from trinus, "threefold") holds that God is three consubstantial persons or hypostases-the Father, the Son (Jesus Christ), and the Holy Spirit-as "one God in three Divine Persons".

Hi there!

The Holy Trinity is immensely important to Christians because it contains the three forms of God; the Father, the Son, and the Holy Spirit.

I'm not sure how much information you need, so if you need more, just ask.; )