This is the beginning of a new part of the story. Luke gives important background information to understand the story. (See: [[rc://en/ta/man/jit/writing-background]])
These were both groups of Jews who had become believers. The writer assumes that the reader understands that these people were all believers because at this point all believers had grown up as Jews. (See: [[rc://en/ta/man/jit/figs-explicit]])
These were believers who had grown up as Jews or become converts living somewhere in the Roman Empire outside of Israel and speaking Greek. Their language and culture were somewhat different from those who had grown up in Israel.
This can be stated in active form. Alternate translation: "the Hebrew believers were overlooking the Grecian widows" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The disciples were able to help the widows because believers were giving money to the apostles [Acts 4:34-35](../04/34.md). Possible meanings are 1) the disciples used the money to buy food, which they would give to the widows, or 2) the disciples gave the money directly to the widows.