In vb.net there is a tooltip contol, in your win form add tooltip control and in code you can write
toolTip.SetToolTip(button1,"Text for tooltip")
When you run program button1 will show 'Text for tooltip'.
Or you can use the property in the properties window. Once you put a tooltip control on a form, all controls on the form will have a tooltip property. Just fill in that field with the text you want the tooltip to display.
Take my love
Take my land
Take me where I cannot stand
I don't care, I'm still free
You can't take the sky from me...