Basically, they are just your way of summarizing all the information you would want to put in each paragraph of an essay. They don't need to be understandable to anyone other than you, but they allow you to make a well structured argument for your point of view, and so gain the best possible marks. For example, if I were to write an essay on the question 'Is Lord Capulet a good father', my plan may be as follows:
Intro:
- patriarchy
- gender roles in rennaissance
- purpose (difficulties, pressures, power, expectations)
P1:
- Gives her relative freedom (renaissance gender roles)
- "ripe to be a bride"
- "within her scope of choice lies my consent"
- "baggage"
- "tallow face"
- she must submit
conc: unreliable
then i'd do 3 more paragraphs and a conclusion, but you get the idea! You may not understand my plan if you don't study Romeo and Juliet, however you can see how I can use my knowledge of quotes (only quotes that either support my main quotes or can be analysed in great detail), context and general knowledge from the play. Hope the year goes well! (I just completed y11)