About dynamic ip and I hope the great God to answer ah !

Our school in some places you can use wireless Internet , and its means of access is the first to provide a mobile wireless connection ( wireless is to use the user name and password authentication ) , and then connect broadband ( also user name and password authentication ) , so you can access the . But I checked it and found ip ( it has several ip address ) , wireless LAN adapter ip 169.254.xx is assigned by the system , which is why ? There , ppp adapter provides an internal network ip, but this is not the host network ip address, what is it used for ? Finally, check the internet ip own words , can be found in a dynamic ip, this is my Internet use ip ip, the ip is where they come from ? ( The attached pictures ) I was a computer science undergraduate , trying to figure out the online mechanism . Hope master wing ,
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I guess
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great God, and worship before the next ,