UI Differece between linux(ubuntu 18.10) and windows(10)?

Hi. I have installed LibreOffice on (ubuntu 18.10), and the UI looks like this:

But, on windows 10 it looks like:

I understand why some ui controls look different (e.g. dropdown lists), But why the icons look different as well?
Thank you.

The Colibre theme has been designed to follow Windows guidelines. The Breeze theme follows KDE guidelines. Thus, they are default on respective platforms to meet the environment the best.

Thanks! only after your answer I realized that the theme could actually be set on:
Tools > Options > LibreOffice > View > Icon Style


Also, as a side note, you might want to consider 18.04 instead of 18.10. The LTS (Long Term Support) versions come out on even years in April. 18.04 LTS is very stable.

I made that mistake with 16.10, had a difficult time with VMware, had to downgrade to 16.04, and couldn’t wait until 18.04 came out (does wonders with Virtualbox).