Put simply, a Visa is an official authorisation that is appended to your passport thus allowing you to travel to, and within, a particular country for a certain fixed period of time.
The rules are different for each and every country and are changing on virtually a daily basis. With this in mind, it is far better to be safe than sorry and you should check out the needs for the country or countries you intend to travel to well in advance of the honeymoon start date.
At the time of booking, your best best is to simply either ask your travel agent, do a little digging on the internet (but be wary of taking any information and advice you read as law!) or, better still, contact the Foreign Embassy for the destination country just to confirm things.
As a general rule of thumb, if it’s a popular tourist destination for that you plan to go to, you are less likely to need a Honeymoon Visa and if it’s somewhere a little of the beaten track then you will. That said, entry requirements for countries are continually tightening and for the sake of five minutes confirming this at time of booking, you will help to ensure that your honeymoon gets a little further than the airport!