Answer:
Sola Fide and Sola Gratia mean, respectively, "Only Faith" and "Only Grace", and can be understood as the way how human is saved by God and ONLY by God. These Solas take out from the Pope and the Priests the possibility to give salvation or to sell it as it was happening.
Step-by-step explanation:
According to Luther, there are five solas that lead to salvation. The difference between Luther's solas and the Catholic theology is that the Solas give to God the duty to save or not humans. In a nutshell, Luther broke the power chain between God and the Authorities (Pope and Priests). With the Solas, he gave to the man their possibility to be saved according to the way they believe in God (Sola Fide), and the grace given ONLY by God, not by men (Sola Gratia).