Get streets distance in osm?

Hey, I'm kinda new at this so bare with me. I downloaded my country osm data and put it in postgres. I would like to make a research on the data so I can for example have all the streets in a radius of 5 miles from a location (ultimately I would like to work directly with the data and not go through external api's. I looked at the data in the roads table and ,in there, there is that column "way" (900913). Can I use the data in that column to reach my goal ? What does the data in that column really represent ? I know it's something related to projection but it's vague.