The New Tax Regime is now the default tax structure in India, offering lower tax rates across most income slabs and a higher basic tax-free threshold, in exchange for giving up almost all the deductions and exemptions available under the old regime — things like 80C, HRA, and home loan interest generally can't be claimed here.
This regime tends to suit people who don't have significant deductions to claim anyway, such as those without a home loan, who don't invest heavily in 80C instruments, or who don't pay rent. Since it's now the default, you have to actively choose the old regime if you want it, typically when filing your return or informing your employer at the start of the financial year. The best choice genuinely depends on your specific income and deduction profile.