The word cracker has several meanings:

1. A thin, crispy baked food, usually made from flour and water, often eaten with cheese or soup. Saltine crackers are square and lightly salted, while graham crackers are sweet and sometimes used to make s'mores.
2. Someone who breaks into computer systems without permission. A cracker tries to bypass security, steal information, or cause damage. This is different from a hacker, a word that can mean someone who solves technical problems and builds things (though people sometimes confuse the two terms). Security experts work hard to stop crackers from breaking into networks and databases.
3. A small explosive that makes a loud pop or bang, like a firecracker on the Fourth of July. In some countries, people pull Christmas crackers at holiday meals: these are decorated paper tubes that snap when pulled apart, releasing small toys and paper crowns inside.

The first meaning is by far the most common one you'll encounter in everyday life. When someone asks you to pass the crackers at dinner, they mean the crispy food, not the computer criminals!