Help on these abbreviations

what does hr mean when speaking bout YouTube views. Also what does Seo mean?

Thanks in advance

SEO stands for search engine optimisation. It's the process of making your site more appealing to search engines, that way your site has a better chance of showing up for more keywords.

High retention (hr) Youtube views are views that retain the audience for a long duration of time. You can read about them in the link below.
http://viewsreviews.org/2016/05/want-buy-high-retention-youtube-views/

Next time you have a question like this, please use Google or search the forum.