In an address, the number is the street number which notes which house on the street is identified. Then, the street name is written which explains the street location. Following that is the city, state and zip code. If you have an address that is 1600 Ashland Avenue W, the house is on Ashland Avenue, but on the western side.
There is most likely an eastern side as well of this avenue. The number 1600 shows the exact house on that street. The house next door would probably be 1602 and 1598. Sometimes, there are streets that are numbered like 38th Avenue, 39th Avenue and 40th Avenue. These streets are located one block apart. They are located in order for each block.