check out this article by Paul Randall: https://www.sqlskills.com/blogs/paul/checkdb-from-every-angle-complete-description-of-all-checkdb-stages/

Also very helpfull is the pluralsight https://app.pluralsight.com/library/courses/sqlserver-database-corruption/description

(i hope i dont break any rules by posting those two links that i consider mandatory for...