What does the Torah mean when it writes "And Hashem saw the B'nei Yisrael"?
Ramban #1 (citing the Ibn Ezra): Hashem saw what the Egyptians were doing to Yisrael in public, and He knew what were doing to them in secret.
Seforno: It means that He took their cries to heart and no longer hid His eyes from them. 1
Targum Onkelos: He saw their enslavement (and took action [Refer to 2:25:2:3).
Targum Yonasan: He saw how they suffered from the slavery.
As the Torah writes later in 3:7 (Seforno).
And what does it mean when it writes "And Hashem knew"?
Rashi and Ramban #2: It means that He took their cries to heart and no longer hid His eyes from them. 1
Ramban #2 (citing the Ibn Ezra): Refer to 2:25:1:1.
Seforno: He knew the plagues of their heart and that their prayers and their cries to Him were uttered with a full heart.
Targum Onkelos: He said verbally that He would redeem them.
Targum Yonasan: It refers to the Teshuvah that they had all done, that, one man did not know about the Teshuvah of the other - but Hashem knew.
As He had until now (Ramban). The Torah refers to the covenant that He made with the Avos, to Yisrael's cries that Hashem heard and their pain that He saw (later, Shemos 3:7), which is why He redeemed them, because, even though the four hundred years had come to an end, they were not worthy of redemption, as the Pasuk writes in Yechezkel (20:8 [Ramban]). Also refer to 2:23:4:1.