Debt Consolidation Loan -Warning

What are the advantages and disadvantages of debt consolidation?
I have two credit cards that I have used over 5 years ago and never paid back. The total of the two cards FIVE YEARS AGO was $1000. Of course, by now, it should be close to $3000 because of all the interests.

What does debt consolidation do? More importantly, can it REALLY remove or reduce the interest that built up over the last 5 years?

When doing a search for debt consolidation services, I get THOUSANDS of results. Which debt consolidation services are better?

Detailed answers would be appreciated.
Update: Am I correct to assume that if I leave the debt as it is, I can have it completely wiped off my credit card two years from now as if it never happened?
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