Running at conversational pace (also called base running), has lots of benefits, including: helps create a more efficient running style; helps your muscles to learn to burn fat more efficiently, receive and process oxygen better, and deal better with lactic acid; trains your heart and lungs to become more efficient at absorbing, delivering, and utilizing oxygen.
As a beginner, most of your runs should be at conversational pace. Don't worry about your pace per mile -- if you can pass the "talk test", you're running at the right speed.
Once you build your fitness level and gain more experience as a runner, you may want to start doing a faster run once a week, such as a fartlek run or a tempo run. But even the most experienced runners don't run every workout at a hard effort. They do easy-paced runs at least every other day to give their bodies a chance to recover and re-build themselves to be stronger. Running hard every day could lead to injury as well as physical and mental burnout from overtraining.
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