WordPress Template Hierarchy:
You should read about WordPress template hierarchy.
This question also has some related answers.
Typical Case:
In your case, the most likely scenario is:
The explainer had set the latest posts as the home page (this is the default option) and you have set a static front page as home page. Since his is blog archive, it's being loaded by index.php
and yours is a page, so that's being loaded by page.php
.
This is just a typical scenario, but there may be other settings that are affecting which template file is being loaded.
Changing the default setting:
If the above is your scenario, then changing the following setting from WordPress wp-admin -> Settings -> Reading -> Your latest posts
(then Save Changes
) will make it the same for you and the explainer. Check the screenshot below:

front-page.php
. If it's not available to load, then WordPress will move ontoindex.php
instead.