Table to Table Relationships Criteria

In the event that it applies to 'all' locations - is that meant that it is one task that only gets worked once and the outcome of that task applies to all locations - or does it mean that each location essentially needs to work that one task individually? In other words - lets say you have 100 locations - if a task applies to 'all' - does that mean just 1 task or is it actually 100 tasks. 

In both cases you're going to essentially have to 'copy' the task in some way for each location no matter what you do. If each location needs it's own unique task - best method is to just have the 'all' task copy itself for each location and related it individually to each. If its only one task and it only 'applies' to each location - then you'll need some kind of intermediary table that joins the task and location in some kind of 'Location Task' setup - whereby you would create the 'task' once - and then create a 'Location Task' for each location (so 100 in total) to join each location to that task. 

The only other option might be IF you just need to see the 'all' tasks. You could just setup a report link on Locations that shows you all tasks that are marked as 'All Locations' and not do any direct relationship between them. This method is just displaying those records so the user thinks they have some kind of relationship but in practice its just a window into the 'all' list. Your tasks that are directly related to a location would show up in one report on the form - while these ones would be a different report on the form.