Short answers, pulled from the story.
Mitosis is the part of the eukaryotic cell cycle in which replicated chromosomes are separated into two genetically identical daughter nuclei. It occurs to enable growth and development from a single fertilized cell, to replace worn-out cells in tissues such as skin and the digestive tract, and to support regeneration in organisms capable of regrowing body parts.
Walther Flemming coined the term "mitosis" in 1882. He derived it from the Greek word mitos, meaning "warp thread," describing the thread-like appearance of chromosomes during division. The Polish histologist Waclaw Mayzel had first formally described the process in animal cells in 1875.
Mitosis proceeds through prophase, prometaphase, metaphase, anaphase, and telophase, followed by the separate process of cytokinesis. Plant cells also have a preceding preprophase stage. During each phase, chromosomes condense, align at the metaphase plate, are pulled apart, and are enclosed in new nuclei.
In open mitosis, typical of animal cells, the nuclear envelope breaks down into small vesicles before chromosomes separate. In closed mitosis, typical of fungi and some protists, chromosomes divide while the nuclear envelope remains intact. A third form, semiopen mitosis, involves partial degradation of the nuclear envelope and is typical of most Apicomplexa.
Errors during mitosis can produce aneuploid cells carrying too few or too many chromosomes, a condition associated with cancer. Mutations arising from mitotic errors can also trigger cancerous growth. In histopathology, the mitotic count is a standard diagnostic marker, and lag-type mitosis is linked to high-risk human papillomavirus infection and cervical cancer.
Mitosis produces two genetically identical daughter cells and maintains the parent cell's chromosome number, while meiosis produces gametes with half the chromosome number and introduces genetic variation. Most human cells are produced by mitosis; sperm and egg cells are produced by meiosis. Meiosis is more complex and may have evolved after mitosis.