Albert Barnes on Hebrews 11:2

For by it. That is, by that faith which gives reality to things hoped for, and a certain persuasion to the mind of the existence of those things which are not seen.

The elders. The ancients; the Hebrew patriarchs and fathers.

Obtained a good report. Literally, "were witnessed of;" that is, an honourable testimony was borne to them in consequence of their faith. The idea is, that their acting under the influence of faith, in the circumstances in which they were, was the ground of the honourable testimony which was borne to them in the Old Testament. See this use of the word in Heb 7:8, and Heb 11:4 of this chapter. Also Lk 4:22, Acts 15:8. In the cases which the apostle proceeds to enumerate in the subsequent part of the chapter, he mentions those whose piety is particularly commended in the Old Testament, and who showed, in trying circumstances, that they had unwavering confidence in God.

(b) "understand" Gen 1:1, Ps 33:6