When the same income is taxable in both India and the US, the India-US DTAA doesn't eliminate tax in either country outright — instead, it specifies a relief mechanism so the two taxes don't simply stack. The two broad mechanisms are the credit method and the exemption method, and which one applies depends on the article of the treaty governing that particular income type.
Credit method
Under the credit method, both countries can tax the income, but your country of residence gives you a credit for tax already paid to the other country — generally capped at what your resident country would have charged on that same income. This is the more common mechanism for income like dividends, interest, and royalties under the India-US treaty, and it's also how the US's domestic Foreign Tax Credit (Form 1116) interacts with treaty-sourced income.
Exemption method
Under the exemption method, one country agrees not to tax income that's taxable in the other, full stop — no residual top-up. This is less common under the India-US treaty than the credit method, but it does apply in specific carve-outs (for example, certain government service or specific categories of independent personal services income, subject to the treaty's exact wording).
Why the mechanism you get matters
A flat exemption and a capped credit can produce very different final tax bills, especially when the two countries' rates diverge. Getting the mechanism wrong — claiming an exemption where only a credit applies, for instance — is a common source of both overpayment and IRS/CBDT scrutiny. The DTAA relief estimator on the DTAA & Tax Residency page walks through the credit-method math for a given income and foreign tax paid; it doesn't attempt to classify which mechanism applies to your specific income type, since that depends on treaty article and your own facts.