The goal of streaking is to Not evenly spread bacteria, so they grow in a thick, continuous layer:

The isolation streak plate technique is specifically designed to separate individual bacterial cells on the surface of an agar plate. By streaking a loop or swab across the agar in a systematic pattern, the bacterial population is progressively diluted, allowing single cells to land apart from each other. These isolated cells then grow into distinct colonies, which can be used for identification, further testing, or pure culture development. This technique is fundamental in microbiology for obtaining pure cultures from mixed bacterial samples, ensuring accurate study of bacterial morphology, physiology, and biochemical characteristics.

Coarse adjustment: The arrow points to the coarse adjustment knob, a large focusing knob on the microscope used to move the stage up or down quickly to bring the specimen into general focus. It is typically used with low-power objective lenses to locate the specimen and obtain an initial image. Using it with high-power lenses can risk damaging the slide or lens because it moves the stage in large increments.

Fine adjustment: A smaller focusing knob that moves the stage very slightly to sharpen the image after the specimen has been brought into general focus. It is mainly used with high-power or oil immersion objectives to achieve precise, clear visualization of cellular details without risking damage to the specimen.