Tithe is different from offering. Tithe is pledging 10% of your monthly earnings. You put it in an envelope with your name on it. Offering is spontaneous donation of any amount of money. An offering bag will be passed around during a sermon and you put your money inside. It's similar to the concept of 'oil money' in a Chinese temple. The only difference is that the 'donation box' in a church is not static; it's passed around and moved around. Offerings are anonymous donations.