Wifi is generally going to be slower than a wired connection. Wifi is subject to device contention as various devices sharing the channel each struggle for bandwidth. There's also, sometimes, the issue of shared channel interference if there are a lot of wireless access points around which will cause some access points to back off and reduce data rates. Wifi is often just slower: [Divide roughly by 10 for Mbit to Mbyte conversion] - 54Mb wifi (best case) == 5.4MB per second. 100Mb wired (best case) == 10MB with no device contention. Many wifi routers now have 1Gb wired links (best case) == 100MB.
Public wifi portals with a password - you're on your own - they all work differently.
For the future: You may find it useful to use Wikipedia / a web search engine to read information on some of this before you come and ask questions on a mailing list. If you can show that you've done some reading / tried something out for yourself before asking a question when you don't understand, it can help other people help you more easily.
http://www.catb.org/~esr/faqs/smart-questions.html may be useful.
All the very best, as ever,
Andy C.