People often mixed up brainstorming and mindmapping.
It's easy to differentiate them.
We can brainstorm about 30 different topics but we can only mindmap about one specific topic.
Brainstorming is gathering individual ideas from group members to produce (creative/unique) ways to solve problems.
We start brainstorming from common ideas or solution and then use it to produce other creative or improved ideas to solve the problems.
For example:
How to use the recycle material.
Normally we would think of solutions like, using both pages of paper, using own grocery bag instead of the shop's plastic bag.
As we slowly improved the ideas, we can come out with creative ideas like, recycle skateboards into guitars, recycle cardboards into furniture and also recycling bottles into pet food.
Picture taken from: http://www.goodnewsnetwork.org/every-bottle-recycling-machine-dispenses-dog-food-strays/