How does my iPhone with no sim receive text messages?

[SpiltBwater]

I am using my Samsung Gio with my Fido Sim card in it.  On Tuesday I took my sim card from my iphone and put it in the Samsung.  Yesterday I sent a request to one of my employees to see availability of if he can work for me this long weekend and had no responce.  Now I get home and have 6 messages on the iphone 1 from my coworker responding that he is unavailible.  How can a phone be able to receive texts with out a sim card?  How does the phone recogonize what the number is supposed to be?  How can a text be sent by one phone and received by another device?  No idea how phones work so is a bit voodoo to me how this happens.

***Edited to add labels***

[Anonymous · Accepted solution]

your phone is not able 2 receive txt with no sim,  but if you look carefulyl at phone, you will see the msg bubble is blue not green,  blue means its an imessage, imessage goes through your wifi not the cellular radio, and wifi works even with no sim card in da phone.  so in reality you receive imessage from someone else because they have iphone too and apple likes to default messages through imessage before the sms gateway if available.