Phosphate glasses containing high loads of rare-earth ions are well-established as laser glass, amplifiers, or waveguides. Studying the structure and chemistry of phosphate glass systems, including the interconnectivity with other elements, is of crucial interest. Phosphates are excellent glass formers that can be combined with many elements, including intermediate oxides such as tellurites or tungstates which are interesting for their high refractive index, high third-order susceptibility, and applications in non-linear optics. Phosphates are also excellent in stabilizing high-ionic glass systems from sulphate-phosphates, to halogenide glasses, including ion-conducting silver iodide containing glasses, or fluoride-phosphate glasses that are used as host matrix for all type of photo-luminescent dopants. Additional applications include such extremes as hazardous waste immobilization or fertilizers, or applications from filter via sealing to bioglasses.