A graduated cylinder is among the most basic pieces of laboratory equipment. With minor variations, they look like this:
_____
\ /
| |
|30-|
| -|
|20-|
| -|
|10-|
| -|
/_____\
Graduated cylinders are made of glass, or a glass-like borosilicate (Pyrex), often with a plastic base.
When reading the volume of a liquid via a graduated cylinder, it's important to remember the meniscus. (Go read about it; I'll be right here.) Thus, consider the following section of a cylinder:
...
| |
| 45----|
|\ /|
| \ 40--/-|
| \________________________/ |
| 35----|
| |
...
What's the volume of this liquid? We must take into account both the meniscus and significant digits. Since you always read from the bottom of the meniscus, we know that the volume is between 35 and 40 mL. Then, since the graduations on the cylinder are only every 5 mL, you estimate the last digit; above, I would estimate the volume to be 36 mL (not 36.4, or anything, since the cylinder isn't that precise).