When you enter a description for the fields in your table the descriptive text appears when you are adding records to a datasheet or form?

No, it does not appear on the datasheet or form. It is really just for design purposes to tell the designer and anyone else that may be changing the design, what the field is for. Sometimes it is very obvious, like Date of Birth or nationality, but sometimes a field may be more obscure, like if it is for some special codes that a company uses to designate products. If you want something on the form, you can use the caption option or type something into a text box beside the field to explain its purpose.