Understanding Train Tickets

You won't be restricted to a particular train with these tickets regardless of what the website is asking you to do. You can also buy these tickets at the station on the day - same cost.

its an accounting of who is passing through

If you give a time for Anytime or Off-Peak you can often also get a seat reservation for that train - but you don't have to use that particular train. However you need to have a good grasp of what other trains your ticket allows you to use. If you pick off-peak, make sure you check - I think some train companies offer a "other trains I can use" function. Off-peak timings vary from route to route & company to company.

Picking a time is a way of ensuring that you pay the right amount (e.g. Whether you're travelling peak or off-peak).

If you don't think you want to travel on a particular train, don't select the option of a seat reservation.

There are no times printed on the tickets themselves in general, as reservations are still separate.

just make sure that you haven't accidentally fallen into an Advance ticket. Advance ones do require travel on a specific train and are valueless on any others, and specifying the time and date gets the offer on a specific train. Advance tickets do need to be purchased in advance but it is a silly name to use - but that's what the government calls it. If you buy an Anytime or Off-Peak before you get to the station that will also be in advance, but not called an Advance ticket.

Make any sense?

Thank you all for your help. It is now crystal clear to me.