as far as supervisors/advisors go, your supervisor is the person who literally supervises your work, i.e. you are 'their' student. the work you do will be directly related to their field of research and area of expertise, and you should go to them for any academic help. they will supervise your research by holding regular meetings with you where you can discuss your work together. they may have come up with the research project, or you may have come up with it yourself and requested to work specifically with them. they are there to guide you through your entire phd, start to finish.
an advisor on the other hand is someone who you can go to for other issues not necessarily regarding your work, eg. other university issues etc. they can be there to mediate if there are problems between you and your supervisor, and should be present at any meetings you have with your supervisor (this is compulsory at my uni but may not apply everywhere). they are basically there as backup if need help with non-academic issues.