Biometric authentication has become a topic of interest ever since there appeared to be a movement toward digital life. However, recent issues regarding social distancing and pandemic control have acted like a catalyst for biometric authentication systems. The majority of companies and organizations accelerated their digital transition journey and tried to provide remote services. Meanwhile, high security digital authentication has become a controversial issue. This paper will present an integrated overview on basic to complicated concepts in biometric systems. Different types of biometric systems, information fusion approaches, spoofing and liveness, and performance evaluation in these systems will be discussed. With respect to the significant importance of anti-spoofing approaches on the reliability of biometric systems, a considerable emphasis is placed on this issue. This review represents the fact that despite all progress made in biometric systems development, unseen attack detection is still a vexing issue in this domain. Cutting edge research paths will be introduced in each topic and an interested reader can, hopefully, find interesting research areas for further study.