This is where you go into detail about what you're going to do in order to achieve your objectives.
Many people who are reading your business plan won't be too interested in the level of detail that you'll get into in the activities section - but it's crucial that you have a clear sense of what you'll need to do to achieve your objectives.
Having a good think about what you'll actually do will also help you to set a more realistic budget - if you try to visualise yourself doing things, you'll find it easier to work out how much it will cost to run your business.
In theory, everything you do should help you to achieve an objective. Of course, real life isn't like that, and you're bound to get involved in some things that achieve absolutely nothing. But if you've got clarity about what you're doing (well defined actitivies) and why you're doing it (clear objectives) then you've got a better chance of keeping on track and achieving your social mission.
For this section, we suggest writing down the key things that you'll need to do to achieve each objective. The level of detail will increase the nearer you get to actual "delivery" - right down to the "to-do" list that you'll have when you're getting on and doing all of this!
And whilst we're on the subject of getting on and doing it, we highly recommend the book Getting things done - which has lots of ideas on how to keep focussed when you've got 100 things to do - which is the usual state that most entrepreneurs find themselves in at start-up stage!