A waiver is “legal forgiveness”, which can be requested if you have a condition, a record, or any other reason why you may be considered “inadmissible” or if you’re in the US “unlawfully” (out of status).
If you’re deemed inadmissible, find the I-601 form and information here.
If you’re unlawfully present (illegal), find the I-601A form and information here.
To file either form, the key is to provide enough evidence (proof) that you should be allowed to enter/stay in the US. If you’re not sure how present your case to USCIS, or if you’ve filed the form and received a Request For Evidence (RFE), contact Lum Law Group for legal assistance.