The nucleolus is located within the nucleus of the cell. It produces the components for ribosomes, which then move out of the nucleus to produce proteins. Cells differ in the amount of protein they need to produce. In cells that have to produce alot of protein, the nucleolus can be as big as a quarter the size of the whole nucleus in order to generate lots of ribosomes.
The nucleolus can be found within the nucleus and does not have a membrane. The nucleolus produces ribosomes, and those ribosomes help synthesize proteins.
Within the nucleus is the nucleolus and it builds ribosomes. Ribosomes are made up of rRNA and a protein. They may be found dispersed in the cytoplasm or attatched to rough endoplasmic reticulum. Ribosomes are essential to cell function because they build many different types of proteins through the process of DNA transcription. For instance if it were not for transport proteins the cell could not recieve essential nutrients.
The link below is very helpful in understanding organelles and what they do.