An important thing to understand when playing Starcraft. When playing as a Zerg, every building and colony you create expands a circle of "living, moving dirt" called the creep. Zergs can only build upon the creep, and it transfers all the resoursces, so your minerals get transported. You can only build a Nydus canal gateway from one creep area to another.

You can expand your creep by building buildings, colonies, and creep colonies, which function as automated defense. Careful, if one is destroyed, the creep falls back.