Exactly - eval, results, and echo are the ones I use most frequently. They affect whether the code is executed, whether the results are shown, and whether the code is shown, respectively. So
```julia; results=false; echo=false
# this code won't show up in the document, but x is available
x = 2
```
```julia; echo=false
# a results block with `5` will show up in the document, but not the code
x + 3
```
```julia; eval=false
# this code block will show up, but won't be evaluated
x = 5
```
```julia
# both this block, and the results (`2`) will show up
x
```