Marketing segmentation, also known as an STP analysis, involves segmenting the market, choosing target segments, and developing positioning strategies. There are 5 key steps: 1) establishing objectives, 2) using segmentation methods like geographic, demographic, psychographic, benefit, and behavioral segmentation, 3) evaluating segment attractiveness based on identifiability, sustainability, reachability, responsiveness, and profitability, 4) selecting target markets using strategies like undifferentiated, differentiated, concentrated, or micromarketing targeting, and 5) developing a positioning strategy by identifying a unique value proposition and choosing a positioning method like value, attributes, symbols, or competition.