What is an EMI filter, RFI EMI filter, Electromagnetic interference filter

 BNX02 Series 12.1 x 9.1 mm 0.00043 Ω 10 A 50 V SMT LC Combined EMI Filter

https://www.futureelectronics.com/p/passives--filters--emi-filters/bnx022-01l-murata-7000770