GEDcompare is a tool to help you see which of the people you have in your GEDCOM are already on WikiTree. You will go through them person by person and look at the matches WikiTree shows you and decide whether or not they match. Once you've gone through the entire report, you will have the opportunity to add any new people in your GEDCOM to WikiTree. A profile will automatically be created, but you will have to "clean" it. Some of the sources and information don't format especially well. It is only one way of creating profiles. The other way is to manually add your people one by one, adding sources, and writing the biography as you go. It's up to you. My personal preference is the manual method, but many people start with the GEDCOM-created profile. You will know after you do one or two by each way which method you prefer.
Now, whether it can help you find your mom's family. I don't know. I do know if you add your information to WikiTree and continue to research you may make connections which can give you more clues to your mom's family. What may help more, though, is getting your and/or your mom's DNA tested and finding people who match. A person who didn't know who her father was found me that way last year and we were able to put together what little she knew to determine that my mom's brother was her father.