Error code P0404 what is the EGR Valve?

Detailed information on troubleshooting and repairing a p0404 automotive trouble code which refers to an EGR circuit range or performance issue

I had the code read and it was P0404 and the recommendation is to clean the exhaust gas recirculation valve and all egr ports

p0404 P0404 - EGR 'A' Control Circuit RangePerformance - OBD2 Trouble code: ✓ Meaning ✓ Causes ✓ Symptoms ✓ Diagnostics ✓ Repair guides ✓ Repair costs ➤ Keep

p0404 P0404 is a generic OBD II fault code that indicates that there is an issue with the Exhaust Gas Recirculation circuit The Engine Control