What is the impact to credit scores of inquiries & what are different categories of inquiries?

A soft inquiry happens when there is no credit decision being considered.

Soft inquiries are never considered as a factor in credit scoring models.

Hard inquiries have a temporary, negative affect on your credit scores. Hard inquiries are rarely the reason you might be denied credit.

Do all inquiries affect the score?
No, the only inquiries that count toward a FICO® Score are those that result from when a consumer actively applies for new credit. The FICO Score does NOT consider:

• Consumer disclosure inquiries — requests made by consumers to obtain a copy of their individual credit report in order to check it.

• Promotional inquiries — requests made by lenders in order to make pre-approved credit offers.

• Account review inquiries — requests made by lenders to review existing accounts with them.

• Employment inquiries — requests marked as coming from employers.

• Insurance inquiries — requests marked as coming from insurance companies.

https://www.experian.com/blogs/ask-experian/credit-education/report-basics/hard-vs-soft-inquiries-on-your-credit-report/

https://www.creditkarma.com/advice/i/hard-credit-inquiries-and-soft-credit-inquiries/

https://www.fico.com/en/blogs/risk-compliance/the-skinny-on-fico-scores-and-inquiries/