What do you call this function in a website?

[aeaez94199182]

I'm new to UX field, and trying to study it. 

There are some websites with this function and I don't know its name.

Part of the website follows the user when the user is scrolling down just like this google search bar.

Is there a name of this function? 

[cmgap · Accepted solution]

Check these out to see  if this is the effect you are looking for:

1. https://helpx.adobe.com/xd/how-to/parallax-effect.html

2. https://www.youtube.com/watch?v=D1W1xZv6RH4

3. https://www.youtube.com/watch?v=YiNZ0dL71TM

If not can  you post a link to an example?