A plan is a method of achieving something that you have worked out in detail beforehand.
The three leaders had worked out a peace plan...
If you plan what you are going to do,you decide in detail what you are going to do,and you intend to do it.
If you plan what you're going to eat,you reduce your chances of overeating...
If you have plans,you are intending to do a particular thing.
'I'm sorry,'she said.'I have plans for tonight.'
When you plan something that you are going to make,build,or create,you decide what the main parts of it will be and do a drawing of how it should be made.
We are planning a new kitchen.
A plan of something that is going to be built or made is a detailed diagram or drawing of it.
...when you have drawn a plan of the garden.