question

Hey,
Ive been working with grasshopper for about 3 months now, but as any biginner..
i have not to familiar with the components under (logic- list and tree).. how would I know when i need to use them..I have the idea that it depends on my design intend...I also go to help within the component but just dont get what they mean...
If anyone can just please breaf explanation on when they are useful?? please.
thank you..