An oblation is a donation or offering to a religious institution. When you offer an oblation at church, you are symbolically presenting it to God.
While the financial donations made by members of a church, temple, or mosque can be thought of as oblations, the word is often used in the context of Catholicism and a few other Christian denominations to mean "gift to God." During the Eucharist ritual in these churches, bread and wine are symbolically offered to God as an oblation. The Latin root of oblation is oblationem, "an offering, presenting, or gift."