Buoys float in the water, anchored to the bottom by a chain or cable. Pylons (or markers) can just be a pole sticking up from the water or land, but may be a more elaborate tower.
These navigational aids have a characteristic color, or display a sign with a background color. They are almost always marked with a number or alphanumeric code. Many display a light which flashes in a set pattern and color. A few have bells or horns.
When leaving a harbor for sea the markers on the port (left) side of the channel will have even numbers displayed on a triangular sign with red background. The markers on the starbord (right) side will have odd numbers displayed on a square sign with green background. The numbers decrease as you move down the channel toward sea, so "3" and "2" are typically the last markers as you leave the channel. Each channel can have it's own set of markers, so the numbers are not unique; San Francisco Bay has many "2" buoys and pylons. Inside small harbors (such as Richardson Bay), many markere are placed and maintained by private groups and may not conform to all of these specifications (esp. the shape of the marker).
In the little maps on this web site some markers may be have been omitted, and information about lights is not indicated. On the official NOAA charts you will find more detail on markers maintained by the Coast Guard. However, private markers, e.g. the markers for the Strawberry channel, may not be indicated at all.