I read about these recently; I am a beginner myself; correct me if I am wrong anywhere!
ISO is image sensor's sensitivity to the light. Usually 100-400 for sunny outdoors, 400-1600 for overcast / evenings / indoor with more light and 1600+ for night / dark indoors. More ISO also means more noise in the image. ISO can be increased to increase the flash range.
Shutter speed is the duration the light is allowed to keep reaching the sensor. This can be used to freeze the action or motion blur etc. Keep it in 1/60 - 1/200 to reduce camera shake / proper flash synch. To freeze water in fountain / falls use 1/500 - 1/4000. For child / animal giving expressions use 1/30 - 1/250. Use tripod for 1/30 and longer