Forms 1095-B and 1095-C report health coverage to employees and the IRS. Applicable large employers and self-funded plans issue them to document who was offered or enrolled in coverage during the year.
If you had Marketplace coverage, use Form 1095-A to complete IRS Form 8962 and reconcile your premium tax credit when you file. It reports your plan and any advance credit paid to your insurer; Form 8962 must be included even if you took no credit in advance.
All three report health coverage for taxes. 1095-A comes from the ACA marketplace (needed to reconcile subsidies), 1095-B comes from insurers/small plans showing you had coverage, and 1095-C comes from large employers (50+) documenting their offer of coverage.