A login form is a form which is used to give access to other form for instance lets take you have a login form and you have two textboxes in login form and a button so if your username textbox and password textbox text is correct then when you click the button you will have access to other forms
make a new form and make another form as well now go to form1 and add two textbox and a button now change the textproperty of button to login now make the form look like this
you can add labels and make the form look good now its time to code