Tithes are monthly donations to the church, usually 10% of your monthly salary. They either get the money in a sealed envelope with your name on it, or auto-deduct from your bank account.
Offerings are anonymous. Offerings are when you seated during a service (or standing up to sing) and an offering bag (or plate) is passed around the congregation, and you take out money from your wallet and put directly inside the offering bag.
There are also numerous other funds for donating money e.g. mission funds, building funds.
What an investment eh? Give all your money for social acceptance among like-minded believers and the promise of a blissful afterlife.