How does the where clause in MySQL work ?

Question

I have a doubt. Assume R and S are 2 relations with attributes A and B respectively . If I have a query
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Select *
From R, S
Where R.A = S.B
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Does this work like a double For Loop in say c or c++
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For( i=0; i<n; i++)
    For( j=0; j<n; j++)
        if (i == j)
           //DO some work
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