Question:
I have been taking communion in my church, but I am not sure I understand it. I know I am not supposed to have any unconfessed sin in my heart when I take it. Other than that, I don't know why it's such an important thing in my church.

Answer:
Instituted by the Lord Jesus Christ Himself - 1 Corinthians 11:23-25
Instituted as a remembrance, not a ritual
Fulfilled the Old Testament type and shadow.
The Old Testament type of communion was Passover.
A commemorative feast celebrated yearly by the Jews in remembrance of their deliverance from Egyptian bondage - Exodus 12:14

Two main elements
1. Flesh of the lamb - Exodus 12:8-9
2. Blood of the lamb - Exodus 12:7, 13

The New Testament fulfillment is Holy Communion
A commemorative feast celebrated as often as believers desire, in remembrance of their deliverance from Satanic bondage - 1 Corinthians 11:24-25

Two main elements - 1 Corinthians 11:26
1. The body of the Lord (bread) was broken from our physical healing
2. The blood of the Lord (fruit of the vine) was shed for the forgiveness of our sin

Some important points about communion
It is a celebration of life, not death
It is for physical healing as well as forgiveness
It can be partaken of as often as desired
The elements of communion are only symbols, not the real thing
Jesus' literal body is in Heaven at the right hand of God - Hebrews 10:12-13
His blood has already been applied for the remission of our sins - Hebrews 9:22-23
Believers should examine themselves before partaking - 1 Corinthians 11:28-30