Fused glass is separate pieces of glass that have been heat bonded together. This is done by layering either multiple pieces of glass, glass frit, or glass powders and heating (through a process of raising and holding the kiln temperatures at various steps) until the glass pieces are bonded together.
However, not all glass can be fused together. Glass with will be fused together must have the same coefficient of thermal expansion (the degree of expansion seen in the glass divided by the temperature). If the glass were to have a different coefficient of thermal expansion, the parts of the glass would expand at a different rate when heated and contract at a different rate when cooled – creating structural pressures on the fused panel.
Fused glass artwork