What are icons?

[RedDuke50]

I apologize if this is in the wrong place. I put it here because I have seen other icon threads being posted.

What exactly are icons? I have been hearing a lot about them on CAF and started wondering what they were.
I heard that they are written by people so is it okay to venerate an icon that is not written by a right person or something?

Thank you

 

[ConstantineTG]

They are windows to heaven where we see the transfigured saints, the Theotokos and Christ in their heavenly glory.

 

[CatholicLife]

They are windows to heaven where we see the transfigured saints, the Theotokos and Christ in their heavenly glory.

Exactly . I can spend hours looking at an icon of The Theotokos of the Passion.

 

[Sam_777]

They are windows to heaven where we see the transfigured saints, the Theotokos and Christ in their heavenly glory.

interesting, this the first time I hear about such thing!, any Catholic reference for that?