What does the fine linen represent in Revelation 19:8?

In Revelation 19:8, the fine linen represents the righteousness, or the positional aspect, of the saints. The bride is granted to be arrayed in fine linen, clean and white, for the fine linen is that righteousness. This points to the saints' positional righteousness.

Les explains that Revelation 19:7-8 describes the marriage of the Lamb and the bride making herself ready. He notes that the word 'wife' is unfortunate; it should be 'bride.' The bride is granted to be arrayed in fine linen, clean and white, and the fine linen is the righteousness—the positional aspect—of the saints. Later in the chapter, Christ comes as King of kings and Lord of lords.

Revelation 19:8

And to her was granted that she should be arrayed in fine linen, clean and white: for the fine linen is the righteousness of saints.

Why is the bride in Revelation depicted as clothed in bright, white, clean linen?

The bride is depicted in bright, white, clean linen because she is presented as a chaste, pure virgin espoused to one husband, Christ. The white clothing symbolizes her purity, matching the whole concept of a virgin bride who has been kept pure for that one husband.