Good wishes to you.
An anti-pope is an usurper of the See of Peter (i.e., Sancta Sedis). That means someone who has been installed invalidly in opposition to the operation the Church has established, or someone who has been elected by a conclave while a current Pope is sitting/enthroned; in essence usurpation is assuming an authority that is not yours. In contrast, Pope Francis was elected after Pope Benedict XVI abdicated the Holy See, and acknowledged universally (by all the living bishops in union with Rome) as Pope. Nothing can take this away from him except death or abdication.