Get 1 page indexed more than 100 times in Google

I have come across two very small websites that appear to have hundreds of pages indexed in Google.
How do they do that?
In Search results for a "site:" search ,Google shows "About 1,200 results" for a site with fewer than 30 pages. Then looking though all the results listed, I found about 200 listings, almost all pointing to the "home" page.
The difference between the listings is that they all have different query strings, with the query strings filled with different keywords.
I would have…
Get 1 page indexed more than 100 times in Google

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