It shows available openings on equipment at various bases that you can bid for if interested. As an example let's say you are a CRJ200 FO in NYC and you want to move to ATL. Once there is a vacancy in ATL on the CRJ200 then you can bid it. Alternatively, you always put what you want in your standing bid and when the vacancy opens and your seniority can hold it, you get awarded that vacancy.