To simplify, this page assumes eucakariotic genomic DNA repeat finding.
Repeat finding can be divided into two tasks, depending on availability of repeat library:
A) Library exists for a given (or possibly closely related species)
B) you construct such library de novo.
Task A is usually a prerequisite step for genome annotation and even blast searches. For newly sequences genomes one should start with B (constructing species specific repeat library).
Detecting known repeats
De novo repeat library construction
For review see: Saha et al. Empirical comparison of ab initio repeat finding programs (2008)