What is polarization in electromagnetic waves?

[captain]

what is it exactly? is it the direction of the electric field when an electromagnetic wave propagates in a certain direction?

 

[genneth]

If you were to measure the E-field at a fixed point as an EM wave moves past, you would find that the field oscillates in a particular direction. That direction is the polarization.

 

[prasannapakkiam]

Well PolArisation is a term used to describe a phenomena found in all Transverse Waves. Now remember that transverse waves move in a direction but their displacement is perpendicular. Now what if these perpendicular displacements were in all directions - i.e. one perpendicular displacement at a certain angle and another at a different one etc. Now Polarisation only let's 1 of those perpendicular displacements through.

I hope I explained clearly. Nevertheless remember that Light is not only made of 1 Plane wave displacement... It is made of multiple ones. Now a Polaroid Polariser let's only one of those Displacements through...

 

[captain]

Well PolArisation is a term used to describe a phenomena found in all Transverse Waves. Now remember that transverse waves move in a direction but their displacement is perpendicular. Now what if these perpendicular displacements were in all directions - i.e. one perpendicular displacement at a certain angle and another at a different one etc. Now Polarisation only let's 1 of those perpendicular displacements through.
I hope I explained clearly. Nevertheless remember that Light is not only made of 1 Plane wave displacement... It is made of multiple ones. Now a Polaroid Polariser let's only one of those Displacements through...

(the underlined part is what i am emphasizing)

which one would it let though or rather how do you determine which will be let through, and also i am unclear about the fact that whether what the polaroid polarizer does is in fact polarization or not?