You can think of this as a square matrix W. The size of the matrix is the size of the vocabulary. If we look at the 100k most frequent words in our corpus, W will be a 100k x 100k matrix.

The value of W(i,j) is the distance between words i and j, and a row of the matrix is the vector representation of that word. Research around word vectors is all about computing W(i,j) in an efficient way that is also useful in natural language processing applications.

Word vectors are often used to compute similarity between words: since words are represented as vectors, we can compute the cosine angle between a given pair of words to find out how similar the two words are.