求助：我刚刚开始学建站，这是人家的一个在线考试系统，我想高手帮我分解下

<%@ Language=VBScript %>
<% option explicit %>
<!--#include file="conn.asp"-->
<% if Request.ServerVariables("http_method")="POST" then   
    if Request.Form("submit")="登    录" then
        '学生登录的处理
           dim rs,sql    
        set rs = server.createobject("adodb.recordset")
                sql="select * from student where studentname='" & Request.Form("studentname") & "' and studentpassword='" & Request.Form("studentpassword") & "'"
                    rs.open sql,conn,1,1
               if err.number<>0 then
        response.write "数据库操作失败："&err.description
               else if rs.bof and rs.eof then
            
                response.write "<center>对不起，请输入正确的用户名和密码。</center>"
                rs.close           
           else        
                            rs.close
                session("studentname")=request.form("studentname")
                set rs=nothing
                call endConnection()
                Response.Redirect "selectsubject.asp"
            
        end if
       end if    
        
        '用户注册
    elseif Request.Form("submit")="注    册" then      
        Response.Redirect "register.asp"
        '管理员进行管理
    elseif Request.Form("submit")="管    理" then
        Response.Redirect "admin/login.asp"        
    end if
end if
%>
这上面的代码是什么意思啊？？能帮助逐句分析下吗？