Yotta is a prefix used with the metric system that is 1024, or 1,000,000,000,000,000,000,000,000 (septillion). A good example of where this prefix is used with computers is with a YB (yottabyte).
What prefix is before a yotta?
A zetta is the prefix used before a yotta.
What comes after a yotta?
As of 2017, a yotta is the largest SI unit and there is no prefix that comes after a yotta.