Question: Can you please elaborate what's "rounded" teaspoon, what's "heaped" teaspoon and what other "types" of teaspoons exists as a measures of volume?

And is there any difference between, rounded teaspoon and rounded teaspoon\**ful*\*?

Answer: 
You have a teaspoon, which measures volume - usually in some ovular, concave measuring device. Let's say you're measuring a teaspoon of something granular, like flour, coffee or sugar.

**1 tsp** (or **1 *level* tsp**) means that the top of what you're measuring is flat; no sugar goes above the top of the spoon.

**1 rounded tsp** means you scoop a spoonful of sugar, and let it form a small pile above the top of the spoon. It is inherently less precise than a level teaspoon.

**1 heaping tsp** means you pretty much try to get as big a pile of sugar onto the spoon as you can, without spilling it. It's a little over a smidgen more than a rounded teaspoon. Helpful hint: Don't try to measure a heaping teaspoon when dealing with liquids.

![enter image description here](https://i.stack.imgur.com/xfZOg.png)  

No, the -ful suffix has no effect on the amount.
There is also the "scant teaspoon" ([example here](http://recipes.howstuffworks.com/tools-and-techniques/what-does-scant-mean.htm)). It's slightly less than a level teaspoon. 

Note that "scant" sometimes means "barely" but in this context it means "not quite."