Faith means to believe in Allah, His angels, His Books, His Messengers, the Last Day, and the Divine Decree, both good and bad.
Prophet Muhammad (peace be upon him)
❝*O you who believe! Keep faith in Allah and His Messenger and the Book which He revealed to His Messenger, and the Book which He revealed before. Whoso disbelieves in Allah, His angels, His Books, and His Messengers and the Last Day, he verily has wandered far astray.*❞
Quran, 4:136