A Br30 light bulb is a type of bulb called a reflector bulb, which is used in general area lighting or directional lighting like track lights. The "Br" in the name refers to the designation of bulged reflector while the 30 is a measurement indicating the diameter of the front of the bulb.
R30 and Br30 light bulbs are almost always interchangeable, since their difference is cosmetic. Both bulbs have a reflective coating on the inside that projects light forward. They can range in price depending on the technology used. They are available as incandescent bulbs, compact fluorescent and halogen.