Polarization refers to the way the RFID signals are emitted from the antenna. A linear polarized antenna emits RFID signals in a straight line on a horizontal or vertical plane. Tag orientation is crucial when using linear polarization. The antenna is only emitting RFID signal on that one plane, so if the tag you are trying to read is not matching that planes orientation your read range could suffer considerably. If the tag is in the correct orientation, a linear polarized antenna will normally have better read range than an antenna using circular polarization. A circular polarized antenna emits the RFID signals in a spiral originating from the center of the antenna. Because of the spiraling nature of the signal, an antenna that is using circular polarization is not affected by orientation as much as one using linear polarization. The tag orientation is not as critical, because the signal is being emitted on multiple planes at once. This is great for increasing read success on items that may not always be in the same position or orientation, but as it is not as focused as a linear signal your maximum read range will suffer. Both antenna types have their purpose in a RFID implementation. If orientation cannot be consistent, a circular polarized antenna is most likely your best bet. If you need more range and consistency is not a problem, than a linear polarized antenna may be a better option for you.