Filter help

dmist98

I recently bought a filter while on holiday. I didn't keep the packaging and now I'm at home struggling to find information about the filter in English on the internet.

I know I'm a total muppet!

Wording on the edge of the filter is "HD-OLux-Day & Night-CPL-77mm".

Any information anyone can give me would be greatly appreciated. If, as I suspect, this is a totally naive question I apologize in advance.

dmist98

Can anyone tell me anything at all about this filter? I'm having no luck on the internet. I'm not really sure how best to use it.

Thanks in advance.

Desertrat48

Sounds like a gradient circular polarizer filter to fit a 77mm lens diameter.