What is the difference between abstract nouns and concrete nouns

Read this excerpt from mohandas gandhi's "banaras hindu university speech." what is the speaker's purpose a. to persuade his audience to struggle for self-governance through peaceful means b. to urge wealthy indians to act instead of merely talk about poverty c. to inform the audience that the british colonial power is stealing indian resources d. to persuade his audience to renounce materialistic wealth and pursue spiritual wealth