No, target market is not same as market segmentation.
Market Segmentation is a marketing process in which you group population on the basis of their geographic location, psychographic features, population demographics or behavioral traits.
Target market is one market segment that the business decides to focus on to service with their products or services.
For example: A business which is into toy making may segment the market on the basis of demographics, may be on the basis of age. Say the segments are 0-6 years, 7 to 16 years, 17 to 24 years and 25+ years.
Now out of these segments the business selects to cater to a particular age group say 0-6 years. This becomes a target market. In case of 0-6 years the 25+ also become a target market because generally for this age group parents are the ones who decide what toy to buy.