difference between mod_ssl & mod_digest

if i want to build a "Secure Website",which module should i use, mod_ssl or mod_digest.

as i know,mod_ssl could providing SSL connection through web,but every client should visit it by "https://xxxxxx",
right? if i edit my index.html to REDIRECT the visitor fro
m "http://xxxxx.com" to "https://xxxxx.com",the client sid
e would auto change normal connection to SSL connection ?

And,mod_digest would only encrypt the "stream code" during
the authorization,after succeed,any HTTP request would sti
ll use Normal "clear text" code to communicate,right ?

please answer my questions,it's very important to me,thank
s a lot.