I earned money for taking classes in my field. What "type" of income is this?

[Hal_Al]

It depends on the details. Who paid you; why did they pay you; what kind of tax form (e.g. 1099-NEC) was issued, etc.

The general rule: side gig money, in your field, is treated as self employment income. Competing general rule: money that pays for education is scholarship.