Brasing is a process which involves a filler metal which has a liquidus > 450°C.

Soldering, on the other hand, involves filler metals with a liquidus of < 450°C (According the American Welding Society (AWS)).

Brazing and soldering is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal.
It then flows over the base metal (known as wetting) and is then cooled to join the work pieces together.

See for more info:

• Hard brazing
• Soft brazing
• Soldering
• Vacuum brazing