drag 'tooltip' control on your form
now on button's "mouse_enter" event
ToolTip1.ToolTipIcon = ToolTipIcon.Info
ToolTip1.BackColor = Color.Khaki
ToolTip1.ForeColor = Color.DarkKhaki
ToolTip1.SetToolTip(button1, "Click me to save data.")
Happy Coding!
:)