怎么理解一下代码

Dim con As New ADODB.Connection
  Dim db_host, db_data, db_user, db_pass, sql As String
  db_host = "localhost"
  db_user = "root"
  db_pass = "wayne119"
  db_data = "wayne"
  con.ConnectionString = "DRIVER={MySQL ODBC 3.51 Driver};" & _
  "SERVER=" & db_host & ";" & _
  "DATABASE=" & db_data & ";" & _
  "UID=" & db_user & ";PWD=" & db_pass & ";" & _
  "OPTION=3;stmt=SET NAMES GB2312"
  con.Open
  Dim rs As New ADODB.Recordset
  sql = "select * from student"
  rs.Open sql, con
  Dim i As Integer
  For i = 1 To rs.Fields.Count
   
  MsgBox i
  Next i
  con.Close

VB.NET code

Dim con As New ADODB.Connection ’申明一个ADO数据库连接对象
  Dim db_host, db_data, db_user, db_pass, sql As String ‘分别定义4个字符串变量，用于进行数据库连接参数。
  db_host = "localhost" ’本地服务器
  db_user = "root"‘用户名
  db_pass = "wayne119"’密码
  db_data = "wayne"‘数据库
'给连接对象的连接字符串进行赋值，连接到指定的服务器
  con.ConnectionString = "DRIVER={MySQL ODBC 3.51 Driver};" & _
  "SERVER=" & db_host & ";" & _
  "DATABASE=" & db_data & ";" & _
  "UID=" & db_user & ";PWD=" & db_pass & ";" & _
  "OPTION=3;stmt=SET NAMES GB2312"
  con.Open ‘打开连接
  Dim rs As New ADODB.Recordset ’申明一个记录集对象
  sql = "select * from student" ’给SQL变量进行赋值，打开学生这个表，进行读取数据
  rs.Open sql, con ’执行Sql语句，将返回的记录保存到记录集中
  Dim i As Integer ‘定义一个整数变量
  For i = 1 To rs.Fields.Count ’对记录说进行循环
    
  MsgBox i ’显示I的值
  Next i
  con.Close ’关闭连接对象