Maggie,
First, Project and Excel are completely different.
Excel is a spreadsheet calculator. You have to tell Excel *everything*
about what you want to compute.
Project is a project calculator. You have to tell it about your
project, using project management nomenclature, to the minimum level of
detail which allows Project "compute" a schedule. It would take you
decades of development time (if ever) to re-develop in Excel what
Project can do for your project.
To answer your question, it's up to you how your organise your projects
in Project. Even if you put them into 25 different Project files, you
can still consolidate them some or all of them together into a "master"
project (with each of the individual projects *inserted* into the
master). [Read about master and subprojects in Help]. Or, you can put
all 25 projects into the same file. Up to you. What you depends on the
number of tasks which define each project, if you'll be asking
individual PMs to maintain their own project files, etc. I guess I
prefer to keep individual files less than 500 tasks (but the actual
limit is massively higher).
I am new to Project but from what I understand in the Tutorial if I have say
25 Projects then I have to set up 25 individual Projects whereas in Excel I
could track them all on one sheet. Is that correct does anyone know?