Giving to God a tithe or "tenth" of our earnings is a commandment - which is followed to show our love for and devotion to Him. We should always pray to Him for guidance before giving.
Giving back to God is an honor and will increase our health, happiness and trust in our Heavenly Father. We are to give back our firstfruits from what He has blessed us each with.
Tithes and offerings support your local church and it's outreach programs, missionaries around the world and those in need in our own communities. "It is better to give than to receive."