JUCollectionView aims to be a drop in replacement for the extremely slow NSCollectionView. Instead of loading every possible cell at once, JUCollectionView only displays the visible cells. To improve the performance even further, JUCollectionView also reuses cells where possible. This means that it only has to load a batch of cells to cover the view and then reuse them its whole lifetime.
Unlike NSCollectionView, JUCollectionView doesn't use NIB instantiating but a approach similar to UITableView on iOS. It asks its data source for a cell (a subclass of JUCollectionViewCell). It also provides identifier and identifier based dequeuing of cells, allowing you to display various kinds of cells while still having the benefit of reusable cells.