Field order/Options??????????

Your camera Canon EOS R shoots progressive.

Just drag a clip into the New Item Icon or into a empty timeline to get a matching sequence:

Make sure you copy entire card to hdd first and ingest via Media Browser.

As for Youtube pick a H.264 preset (you can tweak the bitrate if you want)

https://helpx.adobe.com/premiere-pro/using/interlacing-field-order.html

Old fashioned dv (sd) and hdv camera shoot interlaced.

Nowadays most cameras just shoot progressive.

Which camera do you use and what what will the final desination of you movie be.

Yes it's complicated, so therefore hard to simplify to caveman terms 🙂

However the question to ask yourself is do I even need to worry about it?

Unless there is a pressing need for you to deliver a program interlaced or you are working with interlaced source material - don't!

If at all possible I get my camera people to shoot progressive (not interlaced) and all my post production is progressive too. After Effects renders = progressive, Premiere Pro sequence etc. = all progressive.

The outlier is - any work I do for Network TV is all interlaced output (upper field first). That does not mean the source material is interlaced, though it sometimes is.

None of the above actually answers your question to 'explain' interlacing but being a complex subject please let us know if there is a particluar case you have that requires 'interlacing'. Otherwise - set your project to progressive and live happily ever after 🙂