I don't understand what this regular language is asking for? Find a grammar for L(G) = {w || w | is odd,∑ = (0, 1) }

I don't understand what this regular language is asking for? Find a grammar for L(G) = {w || w | is odd,∑ = (0, 1) }. What does the " || " mean I know a single " | " means or.

Yup, I can see why that would be confusing. The typesetting is probably making this harder to follow. I'm guessing what's written is $$\{w \mid |w| \text{ is odd}, \ldots\}$$. This is the set of all $$w$$ such that $$|w|$$ is odd etc. Here $$|w|$$ typically represents the length of the word $$w$$.
It might have been clearer if the author had used a colon instead of a vertical line in our set builder notation: then it would have been written $$\{w : |w| \text{ is odd}, \ldots\}$$, and maybe it would be easier to see what is going on..