Difference from read_chunk() and source() in a Rmarkdown

Hi, guys! I have a question:

Suppose I have the script example.R and I want to run it inside a .Rmd.

example.R

## ---- chunk
1 + 1

What is the difference from:
example1.Rmd

```{r setup}
knitr::read_chunk("example.R")
``´

```{r chunk}
``´

Than:
example2.Rmd

```{r }
source("example.R")
``´

Thanks a lot!

Ps: I know that there is missing [`] on my example here. I just don't know how to put it better to see here, lol.