Main Street runs N-S along the East Side of Temple Square. It is zero East and zero West. South Temple is the name of the street that runs E-W along the South side of Temple Square. It is zero North and zero South. The second is 200 East, or 2nd East, etc. etc.
Some streets also have names as well.
N-S along the West side of Temple Square. South Temple street runs E-W along the South side of temple Square. South Temple is zero North and zero South. The next street traveling North is 200 North, and on, and on. So, if you are standing in front of the Marriott Hotel on the corner of 1st South and West Temple, you go .65 blocks South.