Floor plans are usually produced so they can be provided to the council when you seek planning permission. The drawings help show the council what proposed works you intend to do when you are asking for the permission as well as what is existing at your property. They can be used to aid with property sales and personal use for future references.
Lease plans are commonly supplied to your solicitor if you are looking to lease out property or commercial space. Lease plans are the same as floor plans but indicate what each room is used for. For instance, if you have a common area in you shop this will be highlighted and labelled. The same applies for your W/C; it will be outlined and labelled. Lease plans are used to show the leaser what the property or space looks like.