What does the symbol B stand for in the periodic table?

The symbol "B" on the periodic table stands for Boron.

Boron is a Group 13 element whose properties place it on the border between metals and nonmetals.  It is a semiconductor, and chemically it is closer to silicon than to aluminum, gallium, indium, and thallium.

The most common sources of boron are tourmaline, borax, and kernite.  Boron is used to produce the color green in pyrotechnics and flares.  It is also used as an ignition source in rockets, and also in nuclear reactors as radiation shields and neutron detectors.  Boron filaments are often used in the aerospace industry because of their light weight and great strength.