Unsupervised learning has no labels, so the feedback signal comes from the structure of the data itself — how well the model groups similar items or compresses the data without losing what matters.
Two common unsupervised goals
Grouping
- Place similar items in the same group
- Signal: how well groups reflect real similarity
- Useful when categories are unknown
Compression
- Reconstruct data from a shorter description
- Signal: how much detail is lost
- Useful for summarizing or denoising
Without labels there is no single correct answer to check against, so judging whether the discovered structure is meaningful usually requires a human or a downstream task.